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Invited talk at the XXXIII International Symposium on Multiparticle Dynamics, Krakow, Poland, 5-11 Sept, 2003. 5 pages, 1 figure Journal-ref: Acta Phys.Polon. B35 (2004) 23-28. We review the recent developments on microscopic transport calculations for two-particle correlations at low relative momenta in ultrarelativistic heavy ion collisions at RHIC.
We enhance the security of Schnorr blind signatures against the novel one-more-forgery of Schnorr [Sc01] andWagner [W02] which is possible even if the discrete logarithm is hard to compute. We show two limitations of this attack. Firstly, replacing the group G by the s-fold direct product G exp(×s) increases the work of the attack, for a given number of signer interactions, to the s-power while increasing the work of the blind signature protocol merely by a factor s. Secondly, we bound the number of additional signatures per signer interaction that can be forged effectively. That fraction of the additional forged signatures can be made arbitrarily small.
Strangeness enhancement is discussed as a feature specific to relativistic nuclear collisions which create a fireball of strongly interacting matter at high energy density. At very high energy this is suggested to be partonic matter, but at lower energy it should consist of yet unknown hadronic degrees of freedom. The freeze-out of this high density state to a hadron gas can tell us about properties of fireball matter. The hadron gas at the instant of its formation captures conditions directly at the QCD phase boundary at top SPS and RHIC energy, chiefly the critical temperature and energy density.
A steep maximum occurs in the Wroblewski ratio between strange and non-strange quarks created in central nucleus-nucleus collisions, of about A=200, at the lower SPS energy square root s approximately equal to 7 GeV. By analyzing hadronic multiplicities within the grand canonical statistical hadronization model this maximum is shown to occur at a baryochemical potential of about 450 MeV. In comparison, recent QCD lattice calculations at finite baryochemical potential suggest a steep maximum of the light quark susceptibility, to occur at similar mu B, indicative of "critical fluctuation" expected to occur at or near the QCD critical endpoint. This endpoint hat not been firmly pinned down but should occur in the 300 MeV < mu c B < 700 MeV interval. It is argued that central collisions within the low SPS energy range should exhibit a turning point between compression/heating, and expansion/cooling at energy density, temperature and mu B close to the suspected critical point. Whereas from top SPS to RHIC energy the primordial dynamics create a turning point far above in epsilon and T, and far below in mu B. And at lower AGS energies the dynamical trajectory stays below the phase boundary. Thus, the observed sharp strangeness maximum might coincide with the critical square root s at which the dynamics settles at, or near the QCD endpoint.
Relativistic nucleus-nucleus collisions create a "fireball" of strongly interacting matter at high energy density. At very high energy this is suggested to be partonic matter, but at lower energy it should consist of yet unknown hadronic, perhaps coherent degrees of freedom. The freeze-out of this high density state to a hadron gas can tell us about properties of fireball matter. Date (v1): Thu, 19 Dec 2002 12:52:34 GMT (146kb) Date (revised v2): Thu, 16 Jan 2003 15:11:47 GMT (146kb) Date (revised v3): Wed, 14 May 2003 12:49:35 GMT (146kb)
The energy dependence of hadron production in central Pb+Pb collisions is presented and discussed. In particular, midrapidity m_T-spectra for pi-, K-, K+, p, bar p, d, phi, Lambda and bar Lambda at 40, 80 and 158 AGeV are shown. In addition Xi and Omega spectra are available at 158 AGeV. The spectra allow to determine the thermal freeze-out temperature T and the transverse flow velocity beta_T at the three energies. We do not observe a significant energy dependence of these parameters; furthermore there is no indication of early thermal freeze-out of Xi and Omega at 158 AGeV. Rapidity spectra for pi-, K-, K+ and phi at 40, 80 and 158 AGeV are shown, as well as first results on Omega rapidity distributions at 158 AGeV. The chemical freeze-out parameters T and mu_B at the three energies are determined from the total yields. The parameters are close to the expected phase boundary in the SPS energy range and above. Using the total yields of kaons and lambdas, the energy dependence of the strangeness to pion ratio is discussed. A maximum in this ratio is found at 40 AGeV. This maximum could indicate the formation of deconfined matter at energies above 40 AGeV. A search for open charm in a large sample of 158 AGeV events is presented. No signal is observed. This result is compared to several model predictions.
Is language the key to number? This article argues that the human language faculty provides the cognitive equipment that enables humans to develop a systematic number concept. Crucially, this concept is based on non-iconic representations that involve relations between relations: relations between numbers are linked with relations between objects. In contrast to this, language-independent numerosity concepts provide only iconic representations. The pattern of forming relations between relations lies at the heart of our language faculty, suggesting that it is language that enables humans to make the step from these iconic representations, which we share with other species, to a generalised concept of number.
Sino-Tibetan is a prime example of how strongly a language family can typologically diversify under the pressure of areal spread features (Matisoff 1991, 1999). One of the manifestation of this is the average length of prosodic words. In Southeast Asia, prosodic words tend to average on one or one-and-a-half syllables. In the Himalayas, by contrast, it is not uncommon to encounter prosodic words containing five to ten syllables. The following pair of examples illustrates this.
Deutsche Fassung: Expertise als soziale Institution: Die Internalisierung Dritter in den Vertrag. In: Gert Brüggemeier (Hg.) Liber Amicorum Eike Schmidt. Müller, Heidelberg, 2005, 303-334.
We discuss the new data for the production of the psi meson in pA collisions at 450 GeV at CERNSPS (of the NA50-collaboration) [1]. We extract from the CERN data sigma(psi'N) 8 mb under the assumption that the psi is produced as a result of the space-time evolution of a point-like c¯c pair which expands with time to the full size of the charmonium state. In the analysis we assume the existence of a relationship between the distribution of color in a hadron and the cross section of its interaction with a nucleon. However, our result is rather sensitive to the pattern of the expansion of the wave packet and significantly larger values of sigma(psi'N)are not ruled out by the data. We show that recent CERN data confirm the suggestion of ref. [2] that color fluctuations of the strengths in charmonium-nucleon interaction are the major source of suppression of the J/psi yield as observed at CERN in both pA and AA collisions.
We introduce a model for the real-time evolution of a relativistic fluid of quarks coupled to non-equilibrium dynamics of the long wavelength (classical) modes of the chiral condensate. We solve the equations of motion numerically in 3+1 spacetime dimensions. Starting the evolution at high temperature in the symmetric phase, we study dynamical trajectories that either cross the line of first-order phase transitions or evolve through its critical endpoint. For those cases, we predict the behavior of the azimuthal momentum asymmetry for highenergy heavy-ion collisions at nonzero impact parameter.
The N/Z ratio of free nucleons from collisions of neutron-rich nuclei as a function of their momentum is studied by means of Isospin dependent Quantum Molecular Dynamics. We find that this ratio is not only sensitive to the form of the density dependence of the symmetry potential energy but also its strength determined by the symmetry energy coe cient. The uncertainties about the symmetry energy coe cient influence the accuracy of probing the density dependence of the symmetry energy by means of the N/Z ratio of free nucleons of neutron-rich nuclei.
Recent calculations applying statistical mechanics indicate that in a setting with compactified large extra dimensions a black hole might evolve into a (quasi-)stable state with mass close to the new fundamental scale M f. Black holes and therefore their relics might be produced at the LHC in the case of extra-dimensional topologies. In this energy regime, Hawking's evaporation scenario is modified due to energy conservation and quantum effects. We reanalyse the evaporation of small black holes including the quantisation of the emitted radiation due to the finite surface of the black hole. It is found that observable stable black hole relics with masses sim 1-3 M f would form which could be identified by a delayed single jet with a corresponding hard momentum kick to the relic and by ionisation, e.g. in a TPC.
The J/psi yield at midrapidity at the top RHIC (relativistic heavy ion collider) energy is calculated within the statistical coalescence model, which assumes charmonium formation at the late stage of the reaction from the charm quarks and antiquarks created earlier in hard parton collisions. The results are compared to the new PHENIX data and to predictions of the standard models, which assume formation of charmonia exclusively at the initial stage of the reaction and their subsequent suppression. Two versions of the suppression scenario are considered. One of them assumes gradual charmonium suppression by comovers, while the other one supposes that the suppression sets in abruptly due to quark-gluon plasma formation. Surprisingly, both versions give very similar results. In contrast, the statistical coalescence model predicts a few times larger J/psi yield in the most central collisions.
Hochschullehre und Neue Medien : Medienkompetenz und Qualifizierungsstrategien für Hochschullehrende
(2003)
Neue Medien halten zunehmend Einzug in den Hochschulalltag und verändern neben dem Arbeitsalltag der Lehrenden auch die Hochschullehre. Neue Medien werden begleitend, unterstützend, ergänzend oder sogar substituierend zu den herkömmlichen Vermittlungs- und Kommunikationsformen in der Lehre eingesetzt. Welche Kompetenzen Hochschullehrende zum Einsatz neuer Medien in der Lehre benötigen, beleuchtet dieser Beitrag. Dabei geht es nicht alleine um den Einsatz von Email und Suchmaschinen des World Wide Web in der eigenen Unterrichtsvorbereitung oder Forschungskooperation, sondern um innovative hochschuldidaktische Ansätze zur Entwicklung neuer Lehr- und Lernmethoden.
We compare quark stars made of color-superconducting quark matter to normal-conducting quark stars. We focus on the most simple color-superconducting system, a two-flavor color superconductor, and employ the Nambu-Jona-Lasinio (NJL) model to compute the gap parameter and the equation of state. By varying the strength of the four-fermion coupling of the NJL model, we study the mass and the radius of the quark star as a function of the value of the gap parameter. If the coupling constant exceeds a critical value, the gap parameter does not vanish even at zero density. For coupling constants below this critical value, mass and radius of a color-superconducting quark star change at most by ca. 20% compared to a star consisting of normal-conducting quark matter. For coupling constants above the critical value mass and radius may change by factors of two or more.
Der Einsatz netzbasierter Diskussionsforen ist in vielen eLearning Szenarien zu finden: in ‚blended learning’ Arrangements wird versucht, durch den Einsatz von Foren netzbasierte Diskussionsprozesse neben den Präsenzsitzungen zu initiieren. Foren werden auch zur in der traditionellen Präsenzlehre eingesetzt, um der Besprechung von Themen Raum und Zeit zu geben, die in den wöchentlichen Präsenzsitzungen zu kurz kommen. Doch vor allem in rein virtueller Lernszenarien spielen netzbasierte Foren eine besondere Rolle: hier dienen sie als virtuelles Plenum der Kommunikation zwischen allen Teilnehmenden und bilden damit eine wichtige Funktion im Rahmen der rein netzbasierten Veranstaltung ab. Trotz dieser vielfältigen Einsatzmöglichkeiten lässt sich im Alltag der Hochschullehre immer wieder das Problem beobachten, dass Studierende die Nutzungsoptionen der Foren nicht auf greifen: Lernende tragen eigene Beiträge nur zögerlich ein und die Rolle und Aufgabe der Foren wird im Rahmen der gesamten Veranstaltung nicht transparent. Dieser Beitrag will hier Abhilfe schaffen: es werden Einsatzszenarien netzbasierter Foren vorgestellt und daneben aus den Erfahrungen mehrerer virtueller Konferenzen Gestaltungsoptionen und Moderationsstrategien für Foren abgeleitet.
Results are presented on event-by-event fluctuations in transverse momentum of charged particles, produced at forward rapidities in p+p, C+C, Si+Si and Pb+Pb collisions at 158 AGeV. Three different characteristics are discussed: the average transverse momentum of the event, the Phi_pT fluctuation measure and two-particle transverse momentum correlations. In the kinematic region explored, the dynamical fluctuations are found to be small. However, a significant system size dependence of Phi_pT is observed, with the largest value measured in peripheral Pb+Pb interactions. The data are compared with predictions of several models. PACS numbers: 14.20.Jn, 13.75.Cs, 12.39.-x
Observation of an exotic S = -2, Q = -2 baryon resonance in proton-proton collisions at the CERN SPS
(2003)
Results of resonance searches in the Xi- pi-, Xi- pi+, antiXi+ pi- and antiXi+ pi+ invariant mass spectra in proton-proton collisions at sqrt s=17.2 GeV are presented. Evidence is shown for the existence of a narrow Xi- pi- baryon resonance with mass of 1.862+/-0.002 GeV/c^2 and width below the detector resolution of about 0.018 GeV/c^2. The significance is estimated to be 4.0 sigma. This state is a candidate for the hypothetical exotic Xi_(3/2)^-- baryon with S = -2, I = 3/2 and a quark content of (d s d s ubar). At the same mass a peak is observed in the Xi- pi+ spectrum which is a candidate for the Xi_(3/2)^0 member of this isospin quartet with a quark content of (d s u s dbar). The corresponding antibaryon spectra also show enhancements at the same invariant mass.
A non-monotonic energy dependence of the K + / pi + ratio with a sharp maximum close to 30 A GeV is observed in central Pb+Pb collisions. Within a statistical model of the early stage, this is interpreted as a sign of the phase transition to a QGP, which causes a sharp change in the energy dependence of the strangeness to entropy ratio. This observation naturally motivates us to study the production of multistrange hyperons (Xi, Omega) as a function of the beam energy. Furthermore it was suggested that the kinematic freeze-out of Omega takes place directly at QGP hadronization. If this is indeed the case, the transverse momentum spectra of the Omega directly reflect the transverse expansion velocity of a hadronizing QGP. In this report we show preliminary NA49 results on Omega - and Omega + production in central Pb+Pb collisions at 40 and 158 A GeV and compare them to measurements of Xi - and Xi + production in central Pb+Pb collisions at 30, 40, 80 and 158 A GeV.
LTAG semantics for questions
(2004)
This papers presents a compositional semantic analysis of interrogatives clauses in LTAG (Lexicalized Tree Adjoining Grammar) that captures the scopal properties of wh- and nonwh-quantificational elements. It is shown that the present approach derives the correct semantics for examples claimed to be problematic for LTAG semantic approaches based on the derivation tree. The paper further provides an LTAG semantics for embedded interrogatives.
Kritik der Gewalt : über den Begriff der Gewalt von Walter Benjamin, Albert Camus und Frantz Fanon
(2004)
Weak function word shift
(2004)
The fact that object shift only affects weak pronouns in mainland Scandinavian is seen as an instance of a more general observation that can be made in all Germanic languages: weak function words tend to avoid the edges of larger prosodic domains. This generalisation has been formulated within Optimality Theory in terms of alignment constraints on prosodic structure by Selkirk (1996) in explaining thedistribution of prosodically strong and weak forms of English functionwords, especially modal verbs, prepositions and pronouns. But a purely phonological account fails to integrate the syntactic licensing conditions for object shift in an appropriate way. The standard semantico-syntactic accounts of object shift, onthe other hand, fail to explain why it is only weak pronouns that undergo object shift. This paper develops an Optimality theoretic model of the syntax-phonology interface which is based on the interaction of syntactic and prosodic factors. The account can successfully be applied to further related phenomena in English and German.
The purpose of this paper is to describe the TüBa-D/Z treebank of written German and to compare it to the independently developed TIGER treebank (Brants et al., 2002). Both treebanks, TIGER and TüBa-D/Z, use an annotation framework that is based on phrase structure grammar and that is enhanced by a level of predicate-argument structure. The comparison between the annotation schemes of the two treebanks focuses on the different treatments of free word order and discontinuous constituents in German as well as on differences in phrase-internal annotation.
Tree-local MCTAG with shared nodes : an analysis of word order variation in German and Korean
(2004)
Tree Adjoining Grammars (TAG) are known not to be powerful enough to deal with scrambling in free word order languages. The TAG-variants proposed so far in order to account for scrambling are not entirely satisfying. Therefore, an alternative extension of TAG is introduced based on the notion of node sharing. Considering data from German and Korean, it is shown that this TAG-extension can adequately analyse scrambling data, also in combination with extraposition and topicalization.
This paper reports on the SYN-RA (SYNtax-based Reference Annotation) project, an on-going project of annotating German newspaper texts with referential relations. The project has developed an inventory of anaphoric and coreference relations for German in the context of a unified, XML-based annotation scheme for combining morphological, syntactic, semantic, and anaphoric information. The paper discusses how this unified annotation scheme relates to other formats currently discussed in the literature, in particular the annotation graph model of Bird and Liberman (2001) and the pie-in-thesky scheme for semantic annotation.
The purpose of this paper is to describe recent developments in the morphological, syntactic, and semantic annotation of the TüBa-D/Z treebank of German. The TüBa-D/Z annotation scheme is derived from the Verbmobil treebank of spoken German [4, 10], but has been extended along various dimensions to accommodate the characteristics of written texts. TüBa-D/Z uses as its data source the "die tageszeitung" (taz) newspaper corpus. The Verbmobil treebank annotation scheme distinguishes four levels of syntactic constituency: the lexical level, the phrasal level, the level of topological fields, and the clausal level. The primary ordering principle of a clause is the inventory of topological fields, which characterize the word order regularities among different clause types of German, and which are widely accepted among descriptive linguists of German [3, 6]. The TüBa-D/Z annotation relies on a context-free backbone (i.e. proper trees without crossing branches) of phrase structure combined with edge labels that specify the grammatical function of the phrase in question. The syntactic annotation scheme of the TüBa-D/Z is described in more detail in [12, 11]. TüBa-D/Z currently comprises approximately 15 000 sentences, with approximately 7 000 sentences being in the correction phase. The latter will be released along with an updated version of the existing treebank before the end of this year. The treebank is available in an XML format, in the NEGRA export format [1] and in the Penn treebank bracketing format. The XML format contains all types of information as described above, the NEGRA export format contains all sentenceinternal information while the Penn treebank format includes only those layers of information that can be expressed as pure tree structures. Over the course of the last year, more fine grained linguistic annotations have been added along the following dimensions: 1. the basic Stuttgart-Tübingen tagset, STTS, [9] labels have been enriched by relevant features of inflectional morphology, 2. named entity information has been encoded as part of the syntactic annotation, and 3. a set of anaphoric and coreference relations has been added to link referentially dependent noun phrases. In the following sections, we will describe each of these innovations in turn and will demonstrate how the additional annotations can be incorporated into one comprehensive annotation scheme.
Davidsonian event semantics has an impressive track record as a framework for natural language analysis. In recent years it has become popular to assume that not only action verbs but predicates of all sorts have an additional event argument. Yet, this hypothesis is not without controversy in particular wrt the particularly challenging case of statives. Maienborn (2003a, 2004) argues that there is a need for distinguishing two kinds of states. While verbs such as sit, stand, sleep refer to eventualities in the sense of Davidson (= Davidsonian states), the states denoted by such stative verbs like know, weigh,and own, as well as any combination of copula plus predicate are of a different ontological type (= Kimian states). Against this background, the present study assesses the two main arguments that have been raised in favour of a Davidsonian approach for statives. These are the combination with certain manner adverbials and Parsons (2000) so-called time travel argument. It will be argued that the manner data which, at first sight, seem to provide evidence for a Davidsonian approach to statives are better analysed as non-compositional reinterpretations triggered by the lack of a regular Davidsonian event argument. As for Parsons´s time travel argument, it turns out that the original version does not supply the kind of support for the Davidsonian approach that Parsons supposed. However, properly adapted, the time travel argument may provide additional evidence for the need of reifying the denotatum of statives, as suggested by the assumption of Kimian states.
This paper sets up a framework for LTAG (Lexicalized Tree Adjoining Grammar) semantics that brings together ideas from different recent approaches addressing some shortcomings of TAG semantics based on the derivation tree. Within this framework, several sample analyses are proposed, and it is shown that the framework allows to analyze data that have been claimed to be problematic for derivation tree based LTAG semantics approaches.
Seit gut einem Jahrzehnt wird in Deutschland gewartet: Auf Literatur wird gewartet, auf den großen Berlin-Roman, auf den großen Nachwende-Roman. Und trotz diverser Romane, die Wiedervereinigung und Berlin zum Thema erhoben, ob nun von Günter Grass oder Thomas Brussig, wird weiter gewartet, kann es anscheinend kein Autor recht machen, wird unterhaltsames Erzählen begehrt oder eine Darstellung auf der Höhe moderner Erzählkunst verlangt. Doch die Alternative ist vielleicht falsch gestellt: Könnte denn nicht ein kunstvoll geschriebener Roman mit präziser und variantenreicher Sprache, ausgeklügelten Erzählstrukturen auch unterhaltsam sein? Schließlich ist Döblins nicht gerade schlichter Roman "Berlin Alexanderplatz" ja auch ein Lesevergnügen, vergleichbar mit "Joyces Ulysses" oder Pynchons "Gravity’s Rainbow". Nun lassen sich solche Romane schlecht wiederholen, hinge jeder Nachahmung des Stils der Verdacht an, Plagiat oder Kopie zu sein. Etwas Ähnliches wäre also immer etwas Anderes, neuartig, artifiziell und darin genaueres Abbild seiner Zeit als die Vielzahl schlichter Romane, die von Berlin oder der Wiedervereinigung erzählen. Nun, in letzter Zeit mehren sich im deutschen Feuilleton Stimmen, die eine gewisse, dementsprechende Kunst des Erzählens bei Ulrich Peltzer ausmachen, weswegen hier die Gelegenheit ergriffen wird, einen Gang durch seine drei letzten Publikationen ["Stefan Martinez", "Alle oder keiner", "Bryant Park"] zu unternehmen, um die Entwicklung derselben darzustellen - im Hinterkopf die Frage: Liegt hier vielleicht schon einer der erwarteten großen Berlin-Romane vor?
Klugheit wird gemeinhin als das Gegenteil von Torheit aufgefasst. Auf diese Weise erfährt sie eine sprachlich vorstrukturierte positive Bewertung und erhält einen ausgezeichneten gesellschaftlichen Status. "Positiv" bedeutet eine Verknüpfung mit spezifischen je gesellschaftlich richtigen Wertmassstäben, die aber in unterschiedlichen Milieus und Regionen durchaus verschieden ausfallen. Diese bilden den impliziten Subtext für die alltägliche Zuschreibung von "Klugheit". Klugheit fokussiert das Verhalten der Menschen, die Handlungen, die Performanz. Klugheit wird denjenigen Personen zugeschrieben, die "das Richtige" tun, und nachdem sie das Richtige getan haben, etabliert sich erst das Kriterium für die Richtigkeit dieser Beurteilung: der Ausgang der Geschichte. Klugheit wird zwar im vornhinein behauptet, stellt sich aber erst im Nachhinein heraus: denn sie misst sich nicht an der vorgeführten Handlung selbst, sondern am Ausgang der "Geschichte". Eine Bauerntochter handelt dann klug, wenn ihre Handlungen zu einem – im Sinne des Erzählers – guten Ende führen, zu einem Happy-End sozusagen. ...
On embedded implicatures
(2004)
The Gricean approach explains implicatures by assumptions about the pragmatics of entire utterances. The phenomenon of embedded implicatures remains a challenge for this approach since in such cases apparently implicatures contribute to the truth-conditional content of constituents smaller than utterances. In this paper, I investigate three areas where embedded implicatures seem to differ from implicatures at the utterance level: optionality, epistemic status, and implicated presuppositions. I conclude that the differences between the two kinds of implicatures justify an approach that maintains Gricean assumptions at the utterance level, and assumes a special operator for embedded implicatures.
Die Ressource "Wissen" rückte in den letzten Jahrzehnten als Quelle wissenschaftlicher Innovation immer stärker ins Zentrum des Interesses. Diese Fokussierung mündete in eine Selbstreflexion der Wissenschaft und der wissenschaftlichen Disziplinen: Thematisiert werden vor allem die Art und Weise, wie Wissen gewonnen wird, sowie die damit zusammenhängende Frage nach der Konstruktion von Wissenschaftlichkeit, womit das Bewusstsein gleichzeitig auf die mehr und mehr sich auflösende Abgrenzung zwischen den Disziplinen beziehungsweise zwischen den drei hauptsächlichen Wissenschaftskulturen, von Natur-, Geistes- und Kultur- sowie Sozialwissenschaften gelenkt wird. Innerhalb und außerhalb der Universitäten bildeten und bilden sich nicht immer klar verortbare "trading zones" (Gallison 1997), in denen neue Formen und Techniken der Wissensproduktion und Wissensvermittlung geprüft, geübt und teilweise auch institutionalisiert werden. ...
The wave function of a spheroidal harmonic oscillator without spin-orbit interaction is expressed in terms of associated Laguerre and Hermite polynomials. The pairing gap and Fermi energy are found by solving the BCS system of two equations. Analytical relationships for the matrix elements of inertia are obtained function of the main quantum numbers and potential derivative. They may be used to test complex computer codes one should develop in a realistic approach of the fission dynamics. The results given for the 240 Pu nucleus are compared with a hydrodynamical model. The importance of taking into account the correction term due to the variation of the occupation number is stressed.
Complex fission phenomena
(2004)
Complex fission phenomena are studied in a unified way. Very general reflection asymmetrical equilibrium (saddle point) nuclear shapes are obtained by solving an integro-differential equation without being necessary to specify a certain parametrization. The mass asymmetry in binary cold fission of Th and U isotopes is explained as the result of adding a phenomenological shell correction to the liquid drop model deformation energy. Applications to binary, ternary, and quaternary fission are outlined.
A very general saddle point nuclear shape may be found as a solution of an integro-differential equation without giving apriori any shape parametrization. By introducing phenomenological shell corrections one obtains minima of deformation energy for binary fission of parent nuclei at a finite (non-zero) mass asymmetry. Results are presented for reflection asymmetric saddle point shapes of thorium and uranium even-mass isotopes with A=226-238 and A=230-238 respectively.
Abstract: The medium modification of kaon and antikaon masses, compatible with low energy KN scattering data, are studied in a chiral SU(3) model. The mutual interactions with baryons in hot hadronic matter and the e ects from the baryonic Dirac sea on the K( ¯K ) masses are examined. The in-medium masses from the chiral SU(3) e ective model are compared to those from chiral perturbation theory. Furthermore, the influence of these in-medium e ects on kaon rapidity distributions and transverse energy spectra as well as the K, ¯K flow pattern in heavy-ion collision experiments at 1.5 to 2 A·GeV are investigated within the HSD transport approach. Detailed predictions on the transverse momentum and rapidity dependence of directed flow v1 and the elliptic flow v2 are provided for Ni+Ni at 1.93 A·GeV within the various models, that can be used to determine the in-medium K± properties from the experimental side in the near future.
Antibaryons bound in nuclei
(2004)
We study the possibility of producing a new kind of nuclear systems which in addition to ordinary nucleons contain a few antibaryons (B = p, , etc.). The properties of such systems are described within the relativistic mean field model by employing G parity transformed interactions for antibaryons. Calculations are first done for infinite systems and then for finite nuclei from 4He to 208Pb. It is demonstrated that the presence of a real antibaryon leads to a strong rearrangement of a target nucleus resulting in a significant increase of its binding energy and local compression. Noticeable e ects remain even after the antibaryon coupling constants are reduced by factor 3 4 compared to G parity motivated values. We have performed detailed calculations of the antibaryon annihilation rates in the nuclear environment by applying a kinetic approach. It is shown that due to significant reduction of the reaction Q values, the in medium annihilation rates should be strongly suppressed leading to relatively long lived antibaryon nucleus systems. Multi nucleon annihilation channels are analyzed too. We have also estimated formation probabilities of bound B + A systems in pA reactions and have found that their observation will be feasible at the future GSI antiproton facility. Several observable signatures are proposed. The possibility of producing multi quark antiquark clusters is discussed. PACS numbers: 25.43.+t, 21.10.-k, 21.30.Fe, 21.80.+a
We investigate the effects of strong color fields and of the associated enhanced intrinsic transverse momenta on the phi-meson production in ultrarelativistic heavy ion collisions at RHIC. The observed consequences include a change of the spectral slopes, varying particle ratios, and also modified mean transverse momenta. In particular, the composition of the production processes of phi-mesons, that is, direct production vs. coalescence-like production, depends strongly on the strength of the color fields and intrinsic transverse momenta and thus represents a sensitive probe for their measurement.
We suggest that the fluctuations of strange hadron multiplicity could be sensitive to the equation of state and microscopic structure of strongly interacting matter created at the early stage of high energy nucleus-nucleus collisions. They may serve as an important tool in the study of the deconfinement phase transition. We predict, within the statistical model of the early stage, that the ratio of properly filtered fluctuations of strange to non-strange hadron multiplicities should have a non-monotonic energy dependence with a minimum in the mixed phase region.
A critical discussion of the present status of the CERN experiments on charm dynamics and hadron collective flow is given. We emphasize the importance of the flow excitation function from 1 to 50 A·GeV: here the hydrodynamic model has predicted the collapse of the v1-flow and of the v2-flow at 10 A·GeV; at 40 A·GeV it has been recently observed by the NA49 collaboration. Since hadronic rescattering models predict much larger flow than observed at this energy we interpret this observation as potential evidence for a first order phase transition at high baryon density B. A detailed discussion of the collective flow as a barometer for the equation of state (EoS) of hot dense matter at RHIC follows. Here, hadronic rescattering models can explain < 30% of the observed elliptic flow, v2, for pT > 2 GeV/c. This is interpreted as evidence for the production of superdense matter at RHIC with initial pressure far above hadronic pressure, p > 1 GeV/fm3. We suggest that the fluctuations in the flow, v1 and v2, should be measured in future since ideal hydrodynamics predicts that they are larger than 50 % due to initial state fluctuations. Furthermore, the QGP coe cient of viscosity may be determined experimentally from the fluctuations observed. The connection of v2 to jet suppression is examined. It is proven experimentally that the collective flow is not faked by minijet fragmentation. Additionally, detailed transport studies show that the awayside jet suppression can only partially (< 50%) be due to hadronic rescattering. We, finally, propose upgrades and second generation experiments at RHIC which inspect the first order phase transition in the fragmentation region, i.e. at µB 400 MeV (y 4 5), where the collapse of the proton flow should be seen in analogy to the 40 A·GeV data. The study of Jet-Wake-riding potentials and Bow shocks caused by jets in the QGP formed at RHIC can give further information on the equation of state (EoS) and transport coe cients of the Quark Gluon Plasma (QGP).
String theory suggests modifications of our spacetime such as extra dimensions and the existence of a mininal length scale. In models with addidional dimensions, the Planck scale can be lowered to values accessible by future colliders. Effective theories which extend beyond the standart-model by including extra dimensions and a minimal length allow computation of observables and can be used to make testable predictions. Expected effects that arise within these models are the production of gravitons and black holes. Furthermore, the Planck-length is a lower bound to the possible resolution of spacetime which might be reached soon.
We present a detailed study of chemical freeze-out in nucleus-nucleus collisions at beam energies of 11.6, 30, 40, 80 and 158A GeV. By analyzing hadronic multiplicities within the statistical hadronization approach, we have studied the strangeness production as a function of centre of mass energy and of the parameters of the source. We have tested and compared different versions of the statistical model, with special emphasis on possible explanations of the observed strangeness hadronic phase space under-saturation. We show that, in this energy range, the use of hadron yields at midrapidity instead of in full phase space artificially enhances strangeness production and could lead to incorrect conclusions as far as the occurrence of full chemical equilibrium is concerned. In addition to the basic model with an extra strange quark non-equilibrium parameter, we have tested three more schemes: a two-component model superimposing hadrons coming out of single nucleon-nucleon interactions to those emerging from large fireballs at equilibrium, a model with local strangeness neutrality and a model with strange and light quark non-equilibrium parameters. The behaviour of the source parameters as a function of colliding system and collision energy is studied. The description of strangeness production entails a non-monotonic energy dependence of strangeness saturation parameter gamma_S with a maximum around 30A GeV. We also present predictions of the production rates of still unmeasured hadrons including the newly discovered Theta^+(1540) pentaquark baryon.
The data on mT spectra of K0S K+ and K- mesons produced in all inelastic p + p and p + pbar interactions in the energy range sqrt(s)NN=4.7-1800GeV are compiled and analyzed. The spectra are parameterized by a single exponential function, dN/(m_T*dm_T)=C exp(-m_T/T), and the inverse slope parameter T is the main object of study. The T parameter is found to be similar for K0S, K+ and K- mesons. It increases monotonically with collision energy from T~30MeV at sqrt(s)NN=4.7GeV to T~220MeV at sqrt(s)NN=1800GeV. The T parameter measured in p+p and p+pbar interactions is significantly lower than the corresponding parameter obtained for central Pb+Pb collisions at all studied energies. Also the shape of the energy dependence of T is different for central Pb+Pb collisions and p+p(pbar) interactions.
We propose a method to experimentally study the equation of state of strongly interacting matter created at the early stage of nucleus--nucleus collisions. The method exploits the relation between relative entropy and energy fluctuations and equation of state. As a measurable quantity, the ratio of properly filtered multiplicity to energy fluctuations is proposed. Within a statistical approach to the early stage of nucleus-nucleus collisions, the fluctuation ratio manifests a non--monotonic collision energy dependence with a maximum in the domain where the onset of deconfinement occurs.
The Kochen-Specker theorem has been discussed intensely ever since its original proof in 1967. It is one of the central no-go theorems of quantum theory, showing the non-existence of a certain kind of hidden states models. In this paper, we first offer a new, non-combinatorial proof for quantum systems with a type I_n factor as algebra of observables, including I_infinity. Afterwards, we give a proof of the Kochen-Specker theorem for an arbitrary von Neumann algebra R without summands of types I_1 and I_2, using a known result on two-valued measures on the projection lattice P(R). Some connections with presheaf formulations as proposed by Isham and Butterfield are made.
Preliminary results on pion-pion Bose-Einstein correlations in central Pb+Pb collisions measured by the NA49 experiment are presented. Rapidity as well as transverse momentum dependence of the HBT-radii are shown for collisions at 20, 30, 40, 80, and 158 AGeV beam energy. Including results from AGS and RHIC experiments only a weak energy dependence of the radii is observed. Based on hydrodynamical models parameters like lifetime and geometrical radius of the source are derived from the dependence of the radii on transverse momentum.
Fluctuations of charged particle number are studied in the canonical ensemble. In the infinite volume limit the fluctuations in the canonical ensemble are different from the fluctuations in the grand canonical one. Thus, the well-known equivalence of both ensembles for the average quantities does not extend for the fluctuations. In view of a possible relevance of the results for the analysis of fluctuations in nuclear collisions at high energies, a role of the limited kinematical acceptance is studied.
The aim of this paper is the exploration of an optimality theoretic architecture for syntax that is guided by the concept of "correspondence": syntax is understood as the mechanism of "translating" underlying representations into a surface form. In minimalism, this surface form is called "Phonological Form" (PF). Both semantic and abstract syntactic information are reflected by the surface form. The empirical domain where this architecture is tested are minimal link effects, especially in the case of "wh"-movement. The OT constraints require the surface form to reflect the underlying semantic and syntactic representations as maximally as possible. The means by which underlying relations and properties are encoded are precedence, adjacency, surface morphology and prosodic structure. Information that is not encoded in one of these ways remains unexpressed, and gets lost unless it is recoverable via the context. Different kinds of information are often expressed by the same means. The resulting conflicts are resolved by the relative ranking of the relevant correspondence constraints.
The argument that I tried to elaborate on in this paper is that the conceptual problem behind the traditional competence/performance distinction does not go away, even if we abandon its original Chomskyan formulation. It returns as the question about the relation between the model of the grammar and the results of empirical investigations – the question of empirical verification The theoretical concept of markedness is argued to be an ideal correlate of gradience. Optimality Theory, being based on markedness, is a promising framework for the task of bridging the gap between model and empirical world. However, this task not only requires a model of grammar, but also a theory of the methods that are chosen in empirical investigations and how their results are interpreted, and a theory of how to derive predictions for these particular empirical investigations from the model. Stochastic Optimality Theory is one possible formulation of a proposal that derives empirical predictions from an OT model. However, I hope to have shown that it is not enough to take frequency distributions and relative acceptabilities at face value, and simply construe some Stochastic OT model that fits the facts. These facts first of all need to be interpreted, and those factors that the grammar has to account for must be sorted out from those about which grammar should have nothing to say. This task, to my mind, is more complicated than the picture that a simplistic application of (not only) Stochastic OT might draw.
A scenario of heavy resonances, called massive Hagedorn states, is proposed which exhibits a fast (t H 1 fm/c) chemical equilibration of (strange) baryons and anti-baryons at the QCD critical temperature Tc. For relativistic heavy ion collisions this scenario predicts that hadronization is followed by a brief expansion phase during which the equilibration rate is higher than the expansion rate, so that baryons and antibaryons reach chemical equilibrium before chemical freeze-out occurs. PACS-Nr.: 12.38.Mh
We study the phase diagram of a generalized chiral SU(3)-flavor model in mean-field approxi- mation. In particular, the influence of the baryon resonances, and their couplings to the scalar and vector fields, on the characteristics of the chiral phase transition as a function of temperature and baryon-chemical potential is investigated. Present and future finite-density lattice calculations might constrain the couplings of the fields to the baryons. The results are compared to recent lattice QCD calculations and it is shown that it is non-trivial to obtain, simultaneously, stable cold nuclear matter.
We show that an unambiguous way of determining the universal limiting fragmentation region is to consider the derivative (d 2 n / d eta 2) of the pseudo-rapidity distribution per participant pair. In addition, we find that the transition region between the fragmentation and the central plateau regions exhibits a second kind of universal behavior that is only apparent in d 2 n / d eta 2. The sqrt s dependence of the height of the central plateau (d n / d eta) eta=0 and the total charged particle multiplicity n total critically depend on the behavior of this universal transition curve. Analyzing available RHIC data, we show that (dn/d eta) eta=0 can be bounded by ln 2 s and n total can be bounded by ln 3 s. We also show that the deuteron-gold data from RHIC has the exactly same features as the gold-gold data indicating that these universal behaviors are a feature of the initial state parton-nucleus interactions and not a consequence of final state interactions. Predictions for LHC energy are also given.
We compare multiplicities as well as rapidity and transverse momentum distributions of protons, pions and kaons calculated within presently available transport approaches for heavy ion collisions around 1 AGeV. For this purpose, three reactions have been selected: Au+Au at 1 and 1.48 AGeV and Ni+Ni at 1.93 AGeV.
System size and centrality dependence of the balance function in A + A collisions at √sNN = 17.2 GeV
(2004)
Electric charge correlations were studied for p+p, C+C, Si+Si and centrality selected Pb+Pb collisions at sqrt s_NN = 17.2$ GeV with the NA49 large acceptance detector at the CERN-SPS. In particular, long range pseudo-rapidity correlations of oppositely charged particles were measured using the Balance Function method. The width of the Balance Function decreases with increasing system size and centrality of the reactions. This decrease could be related to an increasing delay of hadronization in central Pb+Pb collisions.
System size dependence of multiplicity fluctuations of charged particles produced in nuclear collisions at 158 A GeV was studied in the NA49 CERN experiment. Results indicate a non-monotonic dependence of the scaled variance of the multiplicity distribution with a maximum for semi-peripheral Pb+Pb interactions with number of projectile participants of about 35. This effect is not observed in a string-hadronic model of nuclear collision HIJING.
We investigate hadron production and transverse hadron spectra in nucleus-nucleus collisions from 2 A·GeV to 21.3 A·TeV within two independent transport approaches (UrQMD and HSD) based on quark, diquark, string and hadronic degrees of freedom. The enhancement of pion production in central Au+Au (Pb+Pb) collisions relative to scaled pp collisions (the ’kink’) is described well by both approaches without involving a phase transition. However, the maximum in the K+ p+ ratio at 20 to 30 A·GeV (the ’horn’) is missed by ~ 40%. Also, at energies above ~5 A·GeV, the measured K± mT-spectra have a larger inverse slope than expected from the models. Thus the pressure generated by hadronic interactions in the transport models at high energies is too low. This finding suggests that the additional pressure - as expected from lattice QCD at finite quark chemical potential and temperature - might be generated by strong interactions in the early pre-hadronic/partonic phase of central heavy-ion collisions. Finally, we discuss the emergence of density perturbations in a first-order phase transition and why they might affect relative hadron multiplicities, collective flow, and hadron mean-free paths at decoupling. A minimum in the collective flow v2 excitation function was discovered experimentally at 40 A·GeV - such a behavior has been predicted long ago as signature for a first order phase transition.
Let G be a Fuchsian group containing two torsion free subgroups defining isomorphic Riemann surfaces. Then these surface subgroups K and alpha-Kalpha exp(-1) are conjugate in PSl(2,R), but in general the conjugating element alpha cannot be taken in G or a finite index Fuchsian extension of G. We will show that in the case of a normal inclusion in a triangle group G these alpha can be chosen in some triangle group extending G. It turns out that the method leading to this result allows also to answer the question how many different regular dessins of the same type can exist on a given quasiplatonic Riemann surface.
We discuss modifications of the gyromagnetic moment of electrons and muons due to a minimal length scale combined with a modified fundamental scaleMf . First-order deviations from the theoretical standard model value for g-2 due to these String Theory-motivated e ects are derived. Constraints for the new fundamental scale Mf are given.
E-Learning Strategien als Spannungsfeld für Hochschulentwicklung, Kompetenzansätze und Anreizsysteme
(2004)
Dieser Beitrag gibt einen Einstieg in das Thema E-Learning Strategien und zugleich einen Überblick über die Themen, die in den Beiträgen in diesem Band versammelt sind. Anhand der ausführlichen Darstellung der Aspekte, die bei der Strategieentwicklung für den Medieneinsatz zu beachten sind, wird deutlich, in welcher Reihenfolge die hier vorgestellten Beispiele aus Hochschulen zu einem besseren Verständnis für die konzeptionelle und infrastrukturellen Überlegungen im Rahmen einer E-Learning-Gesamtstrategie beitragen. Neben der Einrichtung von Multimedia-Kompetenzzentren und anderen Serviceeinrichtungen sind dies Qualifizierungsangebote, Projektförderungen und begleitende Evaluations- und Beratungsansätze. Der einleitende Beitrag macht zudem deutlich, welche Schritte zur Entwicklung einer solchen Konzeption vorzunehmen, welche Hürden und Aspekte zu beachten sind, um zu einem erfolgreichen, nachhaltigen und geeigneten Medieneinsatz in der Lehre der eigenen Hochschullandschaft zu gelangen und wie Akteure und Zentren frühzeitig in einen solchen Prozess einzubinden sind.
We study the phase diagram of dense, locally neutral three-flavor quark matter as a function of the strange quark mass, the quark chemical potential, and the temperature, employing a general nine-parameter ansatz for the gap matrix. At zero temperature and small values of the strange quark mass, the ground state of matter corresponds to the color-flavor-locked (CFL) phase. At some critical value of the strange quark mass, this is replaced by the recently proposed gapless CFL (gCFL) phase. We also find several other phases, for instance, a metallic CFL (mCFL) phase, a so-called uSC phase where all colors of up quarks are paired, as well as the standard two-flavor color-superconducting (2SC) phase and the gapless 2SC (g2SC) phase.
We discuss gapless colour superconductivity for neutral quark matter in β equilibrium at zero as well as at nonzero temperature. Basic properties of gapless superconductors are reviewed. The current progress and the remaining problems in the understanding of the phase diagram of strange quark matter are discussed.
Report from NA49
(2004)
The most recent data of NA49 on hadron production in nuclear collisions at CERN SPS energies are presented. Anomalies in the energy dependence of pion and kaon production in central Pb+Pb collisions are observed. They suggest that the onset of deconfinement is located at about 30 AGeV. Large multiplicity and transverse momentum fluctuations are measured for collisions of intermediate mass systems at 158 AGeV. The need for a new experimental programme at the CERN SPS is underlined.
Event-by-event fluctuations of particle ratios in central Pb + Pb collisions at 20 to 158 AGeV
(2004)
In the vicinity of the QCD phase transition, critical fluctuations have been predicted to lead to non-statistical fluctuations of particle ratios, depending on the nature of the phase transition. Recent results of the NA49 energy scan program show a sharp maximum of the ratio of K+ to Pi+ yields in central Pb+Pb collisions at beam energies of 20-30 AGeV. This observation has been interpreted as an indication of a phase transition at low SPS energies. We present first results on event-by-event fluctuations of the kaon to pion and proton to pion ratios at beam energies close to this maximum.
Results are presented on event-by-event electric charge fluctuations in central Pb+Pb collisions at 20, 30, 40, 80 and 158 AGeV. The observed fluctuations are close to those expected for a gas of pions correlated by global charge conservation only. These fluctuations are considerably larger than those calculated for an ideal gas of deconfined quarks and gluons. The present measurements do not necessarily exclude reduced fluctuations from a quark-gluon plasma because these might be masked by contributions from resonance decays.
Production of Lambda and Antilambda hyperons was measured in central Pb-Pb collisions at 40, 80, and 158 A GeV beam energy on a fixed target. Transverse mass spectra and rapidity distributions are given for all three energies. The Lambda/pi ratio at mid-rapidity and in full phase space shows a pronounced maximum between the highest AGS and 40 A GeV SPS energies, whereas the anti-Lambda}/pi ratio exhibits a monotonic increase. PACS numbers: 25.75.-q
To be published in J. Phys. G - Proceedings of SQM 2004 : We review the results from the various hydrodynamical and transport models on the collective flow observables from AGS to RHIC energies. A critical discussion of the present status of the CERN experiments on hadron collective flow is given. We emphasize the importance of the flow excitation function from 1 to 50 A.GeV: here the hydrodynamic model has predicted the collapse of the v2-flow ~ 10 A.GeV; at 40 A.GeV it has been recently observed by the NA49 collaboration. Since hadronic rescattering models predict much larger flow than observed at this energy we interpret this observation as evidence for a first order phase transition at high baryon density r b. Moreover, the connection of the elliptic flow v2 to jet suppression is examined. It is proven experimentally that the collective flow is not faked by minijet fragmentation. Additionally, detailed transport studies show that the away-side jet suppression can only partially (< 50%) be due to hadronic rescattering. Furthermore, the change in sign of v1, v2 closer to beam rapidity is related to the occurence of a high density first order phase transition in the RHIC data at 62.5, 130 and 200 A.GeV.
Sprachwahl und Sprachwahrnehmung sind im Deutschen unabdingbar geprägt durch das Wissen von einer Standardsprache. Dieses Wissen basiert für die meisten Sprecher auf der Erfahrung, dass in der Schule manche sprachliche Formen als korrekt, andere als falsch bewertet werden, außerdem auf der Tatsache, dass es Fixierungen der Regeln des Standards in Lexika und Grammatiken gibt. Wissen und Anerkennung dieses Standards sind unabhängig davon, dass keine dieser Kodifikationen unumstritten ist, dass viele Sprecher die Regeln nicht genau kennen und dass als Vorbilder anerkannte Personen (Nachrichtensprecher, Journalisten bestimmter Zeitschriften, Lehrer, Literaten u.a.) keineswegs einheitliche Regeln verfolgen. Der Standard ist fest assoziiert mit der Erfahrung einer legitimen Regelhaftigkeit, also mit Ordnung. Verwendung von Nonstandard wird mit Bezug auf diese Ordnung und von ihr unterschieden wahrgenommen. Diese relationale Sicht der Dinge ist sowohl subjektiv als auch intersubjektiv.
In the last decade, the Penn treebank has become the standard data set for evaluating parsers. The fact that most parsers are solely evaluated on this specific data set leaves the question unanswered how much these results depend on the annotation scheme of the treebank. In this paper, we will investigate the influence which different decisions in the annotation schemes of treebanks have on parsing. The investigation uses the comparison of similar treebanks of German, NEGRA and TüBa-D/Z, which are subsequently modified to allow a comparison of the differences. The results show that deleted unary nodes and a flat phrase structure have a negative influence on parsing quality while a flat clause structure has a positive influence.
This paper develops a framework for TAG (Tree Adjoining Grammar) semantics that brings together ideas from different recent approaches.Then, within this framework, an analysis of scope is proposed that accounts for the different scopal properties of quantifiers, adverbs, raising verbs and attitude verbs. Finally, including situation variables in the semantics, different situation binding possibilities are derived for different types of quantificational elements.
This paper profiles significant differences in syntactic distribution and differences in word class frequencies for two treebanks of spoken and written German: the TüBa-D/S, a treebank of transliterated spontaneous dialogs, and the TüBa-D/Z treebank of newspaper articles published in the German daily newspaper ´die tageszeitung´(taz). The approach can be used more generally as a means of distinguishing and classifying language corpora of different genres.
Multicomponent Tree Adjoining Grammars (MCTAG) is a formalism that has been shown to be useful for many natural language applications. The definition of MCTAG however is problematic since it refers to the process of the derivation itself: a simultaneity constraint must be respected concerning the way the members of the elementary tree sets are added. Looking only at the result of a derivation (i.e., the derived tree and the derivation tree), this simultaneity is no longer visible and therefore cannot be checked. I.e., this way of characterizing MCTAG does not allow to abstract away from the concrete order of derivation. Therefore, in this paper, we propose an alternative definition of MCTAG that characterizes the trees in the tree language of an MCTAG via the properties of the derivation trees the MCTAG licences.
When a statistical parser is trained on one treebank, one usually tests it on another portion of the same treebank, partly due to the fact that a comparable annotation format is needed for testing. But the user of a parser may not be interested in parsing sentences from the same newspaper all over, or even wants syntactic annotations for a slightly different text type. Gildea (2001) for instance found that a parser trained on the WSJ portion of the Penn Treebank performs less well on the Brown corpus (the subset that is available in the PTB bracketing format) than a parser that has been trained only on the Brown corpus, although the latter one has only half as many sentences as the former. Additionally, a parser trained on both the WSJ and Brown corpora performs less well on the Brown corpus than on the WSJ one. This leads us to the following questions that we would like to address in this paper: - Is there a difference in usefulness of techniques that are used to improve parser performance between the same-corpus and the different-corpus case? - Are different types of parsers (rule-based and statistical) equally sensitive to corpus variation? To achieve this, we compared the quality of the parses of a hand-crafted constraint-based parser and a statistical PCFG-based parser that was trained on a treebank of German newspaper text.
Das Zustandspassiv : grammatische Einordnung – Bildungsbeschränkungen – Interpretationsspielraum
(2005)
“Comments are very welcome!” This basic attitude and the many ways of implementing it contribute immensely to the fascination of engaging in scientific research. I am grateful to Theoretical Linguistics for providing a public platform for this kind of scholarly exchange and I thank all commentators for their thoughtful, stimulating, and often challenging contributions to my target article. My response will address two main issues that are raised by the commentaries. The first issue is shaped by a cluster of questions relating to ontology. The second issue concerns questions of methodology pertaining in particular to the problem of judging data.
Since Donald Davidson’s seminal work “The Logical Form of Action Sentences” (1967) event arguments have become an integral component of virtually every semantic theory. Over the past years Davidson´s proposal has been continuously extended such that nowadays event(uality) arguments are generally associated not only with action verbs but with predicates of all sorts. The reasons for such an extension are seldom explicitly justified. Most problematical in this respect is the case of stative expressions. By taking a closer look at copula sentences the present study assesses the legitimacy of stretching the Davidsonian notion of events and discusses its consequences. A careful application of some standard eventuality diagnostics (perception reports, combination with locative modifiers and manner adverbials) as well as some new diagnostics (behavior of certain degree adverbials) reveals that copular expressions do not behave as expected under a Davidsonian perspective: they fail all eventuality tests, regardless of whether they represent stage-level or individual-level predicates. In this respect, copular expressions pattern with stative verbs like know, hate, and resemble, which in turn differ sharply from state verbs like stand, sit, and sleep. The latter pass all of the eventuality tests and therefore qualify as true “Davidsonian state” expressions. On the basis of these empirical observations and taking up ideas of Kim (1969, 1976) and Asher (1993, 2000), an alternative account of copular expressions (and stative verbs) is provided, according to which the copula introduces a referential argument for a temporally bound property exemplification (= “Kimian state”). Considerations on some logical properties, viz. closure conditions and the latent infinite regress of eventualities, suggest that supplementing Davidsonian eventualities with Kimian states may yield not only a more adequate analysis of copula sentences but also a better understanding of eventualities in general.
Der Autor beschäftigt sich u. a. mit den Fragen: Welchen Stellenwert haben unsere literarischen Bildungsgüter in der Mediengesellschaft? Stehen Goethe und Schiller, das Dioskurenpaar der deutschen Klassik, noch fest auf dem Weimarer Sockel, oder zerbröselt dieser zum Sanierungsfall, en passant besucht auf Klassenfahrten, von denen nur das ins heimische Bücherregal wandert, was leicht faßlich ist?
Während der Brief in Zeiten von persönlichen Krisen und Konflikten mancherlei Unannehmlichkeiten aus dem Kommunikationsweg räumt, stellt der Kontext Krieg für das Briefeschreiben in vielerlei Hinsicht eine Herausforderung dar. Der Privatbrief (Epistula familiaris) ist in der ersten Hälfte des 20. Jahrhunderts in Westeuropa – das heisst auch zur Zeit des 2. Weltkriegs – das wichtigste Medium informeller Distanzkommunikation, welche im Allgemeinen durch Inoffizialität und Spontaneität, durch Individualität und Vertraulichkeit gekennzeichnet ist. In der Regel ist der Privatbrief im juristischen Sinne nicht verfügbar. Ein Kennzeichen ist somit auch seine Nichtreproduzierbarkeit. Neben der thematischen Offenheit macht sich meist eine stärkere stilistische Freiheit bemerkbar. Zeichen von Flüchtigkeit oder Sorgfalt sind ausser den Formalia des Datums, der Anrede, des Textkörpers und der Unterschrift, über das geschriebene Wort hinaus nonverbale Informationen wie die Lesbarkeit der Schrift, die Wahl des Papiers, Schreibwerkzeug sowie die Länge eines Briefes (vgl. Ermert 1979, Nickisch 1991, Beyer/ Täubrich 1996, Zott 2003). Der Privatbrief wird zwar im graphischen Medium der Schrift realisiert, steht aber stilistisch der konzeptionellen "Mündlichkeit" näher. (Koch/ Oesterreicher 1994, 587) Der private Briefwechsel wird spontan aufgenommen und kann in der Regel ohne Zwang abgebrochen werden (vgl. Zott 2003). ...
Wer sich einmal in Deutschschweizer IRC-Chatkanälen herumgesehen hat, hat sofort bemerkt, dass neben der Standardsprache häufig Mundart verwendet wird. Eine Analyse der Varietätenverwendung bietet sich an. Es stellt sich die Frage: was bedeutet sprachliche Norm in einem Kommunikationsraum, in dem die Vorgabe, Deutsch zu schreiben, nur heißt nicht Französisch, Italienisch, Türkisch, Serbisch, Portugiesisch usw. zu schreiben, wo also die Standardsprache nur eine der akzeptierten Varietäten ist? Was bedeutet sprachliche Norm, wo Berndeutsch mit /l/-Vokalisierung neben Walliserdeutsch mit archaischen Volltonvokalen in Nebensilben vorkommt, wo für ein standardsprachliches [a:] ‹a, ah, aa, o, oh› oder ‹oo› stehen kann? Der Frage nach einer deskriptiven Norm wird hier nachgegangen, indem Möglichkeiten der Verschriftung einzelner Aspekte aufgezeigt werden und deren Nutzung in regionalen und überregionalen Chaträumen verglichen werden. Aus dem aktuellen Gebrauch wird dann versucht implizite Normen abzuleiten.
We analyze longitudinal pion spectra from E_lab= 2AGeV to sqrt s_NN=200GeV within Landau's hydrodynamical model. From the measured data on the widths of the pion rapidity spectra, we extract the sound velocity c_s in the early stage of the reactions. It is found that the sound velocity has a local minimum (indicating a softest point in the equation of state, EoS) at E_beam=30AGeV. This softening of the EoS is compatible with the assumption of the formation of a mixed phase at the onset of deconfinement.
Within the scenario of large extra dimensions, the Planck scale is lowered to values soon accessible. Among the predicted effects, the production of TeV mass black holes at the LHC is one of the most exciting possibilities. Though the final phases of the black hole’s evaporation are still unknown, the formation of a black hole remnant is a theoretically well motivated expectation. We analyze the observables emerging from a black hole evaporation with a remnant instead of a final decay. We show that the formation of a black hole remnant yields a signature which differs substantially from a final decay. We find the total transverse momentum of the black hole event to be significantly dominated by the presence of a remnant mass providing a strong experimental signature for black hole remnant formation.
Potential energy surfaces are calculated by using the most advanced asymmetric two-center shell model allowing to obtain shell and pairing corrections which are added to the Yukawa-plus-exponential model deformation energy. Shell effects are of crucial importance for experimental observation of spontaneous disintegration by heavy ion emission. Results for 222Ra, 232U, 236Pu and 242Cm illustrate the main ideas and show for the first time for a cluster emitter a potential barrier obtained by using the macroscopic-microscopic method.
The D-meson spectral density at finite temperature is obtained within a self-consistent coupled-channel approach. For the bare meson-baryon interaction, a separable potential is taken, whose parameters are fixed by the position and width of the Lambda_c (2593) resonance. The quasiparticle peak stays close to the free D-meson mass, indicating a small change in the effective mass for finite density and temperature. However, the considerable width of the spectral density implies physics beyond the quasiparticle approach. Our results indicate that the medium modifications for the D-mesons in nucleus-nucleus collisions at FAIR (GSI) will be dominantly on the width and not, as previously expected, on the mass.
We study the effects of isovector-scalar meson delta on the equation of state (EOS) of neutron star matter in strong magnetic fields. The EOS of neutron-star matter and nucleon effective masses are calculated in the framework of Lagrangian field theory, which is solved within the mean-field approximation. From the numerical results one can find that the delta-field leads to a remarkable splitting of proton and neutron effective masses. The strength of delta-field decreases with the increasing of the magnetic field and is little at ultrastrong field. The proton effective mass is highly influenced by magnetic fields, while the effect of magnetic fields on the neutron effective mass is negligible. The EOS turns out to be stiffer at B < 10^15G but becomes softer at stronger magnetic field after including the delta-field. The AMM terms can affect the system merely at ultrastrong magnetic field(B > 10^19G). In the range of 10^15 G - 10^18 G the properties of neutron-star matter are found to be similar with those without magnetic fields.
Results are presented from a search for the decays D0 -> K min pi plus and D0 bar -> K plus pi min in a sample of 3.8x10^6 central Pb-Pb events collected with a beam energy of 158A GeV by NA49 at the CERN SPS. No signal is observed. An upper limit on D0 production is derived and compared to predictions from several models.
We study Mach shocks generated by fast partonic jets propagating through a deconfined strongly-interacting matter. Our main goal is to take into account different types of collective motion during the formation and evolution of this matter. We predict a significant deformation of Mach shocks in central Au+Au collisions at RHIC and LHC energies as compared to the case of jet propagation in a static medium. The observed broadening of the near-side two-particle correlations in pseudorapidity space is explained by the Bjorken-like longitudinal expansion. Three-particle correlation measurements are proposed for a more detailed study of the Mach shock waves.
Nuclear collisions at intermediate, relativistic, and ultra-relativistic energies offer unique opportunities to study in detail manifold fragmentation and clustering phenomena in dense nuclear matter. At intermediate energies, the well known processes of nuclear multifragmentation -- the disintegration of bulk nuclear matter in clusters of a wide range of sizes and masses -- allow the study of the critical point of the equation of state of nuclear matter. At very high energies, ultra-relativistic heavy-ion collisions offer a glimpse at the substructure of hadronic matter by crossing the phase boundary to the quark-gluon plasma. The hadronization of the quark-gluon plasma created in the fireball of a ultra-relativistic heavy-ion collision can be considered, again, as a clustering process. We will present two models which allow the simulation of nuclear multifragmentation and the hadronization via the formation of clusters in an interacting gas of quarks, and will discuss the importance of clustering to our understanding of hadronization in ultra-relativistic heavy-ion collisions.
Using CORSIKA for simulating extensive air showers, we study the relation between the shower characteristics and features of hadronic multiparticle production at low energies. We report about investigations of typical energies and phase space regions of secondary particles which are important for muon production in extensive air showers. Possibilities to measure relevant quantities of hadron production in existing and planned accelerator experiments are discussed.
The regeneration of hadronic resonances is discussed for heavy ion collisions at SPS and SIS-300 energies. The time evolutions of Delta, rho and phi resonances are investigated. Special emphasize is put on resonance regeneration after chemical freeze-out. The emission time spectra of experimentally detectable resonances are explored.
The recently proposed baryon-strangeness correlation (C_BS) is studied with a string-hadronic transport model (UrQMD) for various energies from E_lab=4 AGeV to \sqrt s=200 AGeV. It is shown that rescattering among secondaries can not mimic the predicted correlation pattern expected for a Quark-Gluon-Plasma. However, we find a strong increase of the C_BS correlation function with decreasing collision energy both for pp and Au+Au/Pb+Pb reactions. For Au+Au reactions at the top RHIC energy (\sqrt s=200 AGeV), the C_BS correlation is constant for all centralities and compatible with the pp result. With increasing width of the rapidity window, C_BS follows roughly the shape of the baryon rapidity distribution. We suggest to study the energy and centrality dependence of C_BS which allow to gain information on the onset of the deconfinement transition in temperature and volume.
Trapping black hole remnants
(2005)
Large extra dimensions lower the Planck scale to values soon accessible. The production of TeV mass black holes at the LHC is one of the most exciting predictions. However, the final phases of the black hole's evaporation are still unknown and there are strong indications that a black hole remnant can be left. Since a certain fraction of such objects would be electrically charged, we argue that they can be trapped. In this paper, we examine the occurrence of such charged black hole remnants. These trapped remnants are of high interest, as they could be used to closely investigate the evaporation characteristics. Due to the absence of background from the collision region and the controlled initial state, the signal would be very clear. This would allow to extract information about the late stages of the evaporation process with high precision.