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The paper proposes a variation of simulation for checking and proving contextual equivalence in a non-deterministic call-by-need lambda-calculus with constructors, case, seq, and a letrec with cyclic dependencies. It also proposes a novel method to prove its correctness. The calculus' semantics is based on a small-step rewrite semantics and on may-convergence. The cyclic nature of letrec bindings, as well as non-determinism, makes known approaches to prove that simulation implies contextual equivalence, such as Howe's proof technique, inapplicable in this setting. The basic technique for the simulation as well as the correctness proof is called pre-evaluation, which computes a set of answers for every closed expression. If simulation succeeds in finite computation depth, then it is guaranteed to show contextual preorder of expressions.
We develop a multivariate generalization of the Markov–switching GARCH model introduced by Haas, Mittnik, and Paolella (2004b) and derive its fourth–moment structure. An application to international stock markets illustrates the relevance of accounting for volatility regimes from both a statistical and economic perspective, including out–of–sample portfolio selection and computation of Value–at–Risk.
An asymmetric multivariate generalization of the recently proposed class of normal mixture GARCH models is developed. Issues of parametrization and estimation are discussed. Conditions for covariance stationarity and the existence of the fourth moment are derived, and expressions for the dynamic correlation structure of the process are provided. In an application to stock market returns, it is shown that the disaggregation of the conditional (co)variance process generated by the model provides substantial intuition. Moreover, the model exhibits a strong performance in calculating out–of–sample Value–at–Risk measures.
This paper documents and studies sources of international differences in participation and holdings in stocks, private businesses, and homes among households aged 50+ in the US, England, and eleven continental European countries, using new internationally comparable, household-level data. With greater integration of asset and labor markets and policies, households of given characteristics should be holding more similar portfolios for old age. We decompose observed differences across the Atlantic, within the US, and within Europe into those arising from differences: a) in the distribution of characteristics and b) in the influence of given characteristics. We find that US households are generally more likely to own these assets than their European counterparts. However, European asset owners tend to hold smaller real, PPP-adjusted amounts in stocks and larger in private businesses and primary residence than US owners at comparable points in the distribution of holdings, even controlling for differences in configuration of characteristics. Differences in characteristics often play minimal or no role. Differences in market conditions are much more pronounced among European countries than among US regions, suggesting significant potential for further integration.
Marginal income taxes may have an insurance effect by decreasing the effective fluctuations of after-tax individual income. By compressing the idiosyncratic component o personal income fluctuations, higher marginal taxes should be negatively correlated with the dispersion of consumption across households, a necessary implication of an insurance effect of taxation. Our study empirically examines this negative correlation, exploiting the ample variation of state taxes across US states. We show that taxes are negatively correlated with the consumption dispersion of the within-state distribution of non-durable consumption and that this correlation is robust.
Based on a unique dataset of legislative changes in industrial countries, we identify events that strengthen the competition control of mergers and acquisitions, analyze their impact on banks and non-financial firms and explain the different reactions observed with specific regulatory characteristics of the banking sector. Covering nineteen countries for the period 1987 to 2004, we find that more competition-oriented merger control increases the stock prices of banks and decreases the stock prices of non-financial firms. Bank targets become more profitable and larger, while those of non-financial firms remain mostly unaffected. A major determinant of the positive bank returns is the degree of opaqueness that characterizes the institutional setup for supervisory bank merger reviews. The legal design of the supervisory control of bank mergers may therefore have important implications for real activity.
This work is devoted to the description of mechanisms that might be responsible for avian magnetoreception. Two possible theoretical concepts underlying this phenomenon are formulated and their functionality is proven in realistic geomagnetic fields. It has been suggested that the "magnetic sense" in birds may be mediated by the blue light receptor protein- cryptochrome- which is known to be localized in the retinas of migratory birds. Cryptochromes are a class of photoreceptor signaling proteins that are found in a wide variety of organisms and which primarily perform regulatory functions, such as the entrainment of circadian rhythm in mammals and the inhibition of hypocotyl growth in plants. Recent experiments have shown that the activity of cryptochrome-1 in Arabidopsis thaliana is enhanced by the presence of a weak external magnetic field, confirming the ability of cryptochrome to mediate magnetic field responses. Cryptochrome's signaling is tied to the photoreduction of an internally bound chromophore, flavin adenine dinucleotide (FAD). The spin chemistry of this photoreduction process, which involves electron transfer from a chain of three tryptophans, is modulated by the presence of a magnetic field in an effect known as the radical pair mechanism. Cryptochrome was suggested as a possible magnetoreceptor for the first time in 2000. However, no realistic calculations of the magnetic field effect in cryptochrome were performed. One of the goals of the present thesis is computationally to study the electron spin dynamics in cryptochrome and to show the feasibility of a cryptochrome-based compass in birds. In particular, the activation yield of cryptochrome was studied as a function of an external magnetic field and it was shown that the activation of the protein can be influenced by the geomagnetic field. In the work it has also been proven that cryptochrome provides an inclination compass, which is necessary for bird orientation. The evolution of spin densities as a function of time is also discussed. An alternative mechanism of avian magnetoreception discussed in the thesis is based on the interaction of two iron minerals (magnetite and maghemite) which were only recently found in subcellular compartments within the sensory dendrites of the upper beak of several bird species. The iron minerals in the beak form platelets of crystalline maghemite and assemblies of magnetite nanoparticles (magnetite clusters). The interaction between these particles can be manipulated by an external magnetic field inducing a primary receptor potential via strain-sensitive membrane channels that lead to a certain bird orientation effect. Various properties of the magnetite/maghemite magnetoreceptor system have been considered: the potential energy surface of the magnetite cluster has been calculated and analyzed as a function of the orientation of an external magnetic field; the forces acting on the magnetite cluster were calculated and analyzed; the force differences caused by the change of the direction of external magnetic field were established; the probability of opening the mechanosensitive ion channel was calculated. Finally it has been demonstrated that the iron-mineral based magnetoreceptor provides a polarity magnetic compass. Various conditions at which the magnetoreception process is violated are outlined.
Strong chromofields developed at early stages of relativistic heavy-ion collisions give rise to the collective deceleration of net baryons from colliding nuclei. We have solved classical equations of motion for baryonic slabs under the action of time-dependent chromofield. We have studied sensitivity of the slab trajectories and their final rapidities to the initial strength and decay pattern of the chromofield as well as to the back reaction of produced plasma. This mechanism can naturally explain significant baryon stopping observed at RHIC, an average rapidity loss hδyi ≈ 2. Using a Bjorken hydrodynamical model with particle producing source we also study the evolution of partonic plasma produced as the result of chromofield decay. Due to the delayed formation and expansion of plasma its maximum energy density is much lower than the initial energy density of the chromofield. It is shown that the net-baryon and produced parton distributions are strongly correlated in the rapidity space. The shape of net-baryon spectra in midrapidity region found in the BRAHMS experiment cannot be reproduced by only one value of chromofield energy density parameter ǫ0, even if one takes into account novel mechanisms as fluctuations of color charges generated on the slab surface, and weak interaction of baryon-rich matter with produced plasma. The further step to improve our results is to take into account rapidity dependence of saturation momentum as explained in thesis. Different values of parameter ǫ0 has been tried for different variants of chromofield decay to fit BRAHMS data for net-baryon rapidity distribution. In accordance with our analysis, data for fragmentation region correspond to the lower chromofield energy densities than mid-rapidity region. χ2 analysis favors power-law of chromofield decay with corresponding initial chromofield energy density of order ǫf = 30GeV/fm3.
In the article, a travel sketch of Danish playwright Kaj Munk (1898 – 1944) is analytically considered. The analysis of this text allows drawing at least three conclusions: 1. Explicit motive of seasickness, figuring here as antithetic modification of implicite present free-standing posture motive, symbolizes idea of disintegrating personality. 2. Such a symbolism is deeply rooted in that of Danish identity. 3. From literary styles and trends history point of view, the sketch appears to be typical of that line in expressionism, which continues tradition of symbolism as artistic and literary trend of late 19th century.
Many older US households have done little or no planning for retirement, and there is a substantial population that seems to undersave for retirement. Of particular concern is the relative position of older women, who are more vulnerable to old-age poverty due to their longer longevity. This paper uses data from a special module we devised on planning and financial literacy in the 2004 Health and Retirement Study. It shows that women display much lower levels of financial literacy than the older population as a whole. In addition, women who are less financially literate are also less likely to plan for retirement and be successful planners. These findings have important implications for policy and for programs aimed at fostering financial security at older ages.