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Institute
The Karl Schwarzschild Meeting 2017 (KSM2017) has been the third instalment of the conference dedicated to the great Frankfurter scientist, who derived the first black hole solution of Einstein's equations about 100 years ago.
The event has been a 5 day meeting in the field of black holes, AdS/CFT correspondence and gravitational physics. Like the two previous instalments, the conference continued to attract a stellar ensemble of participants from the world's most renowned institutions. The core of the meeting has been a series of invited talks from eminent experts (keynote speakers) as well as the presence of plenary research talks by students and junior speakers.
List of Conference photo and poster, Sponsors and funding acknowledgments, Committees and List of participants are available in this PDF.
In this Letter we study the radiation measured by an accelerated detector, coupled to a scalar field, in the presence of a fundamental minimal length. The latter is implemented by means of a modified momentum space Green's function. After calibrating the detector, we find that the net flux of field quanta is negligible, and that there is no Planckian spectrum. We discuss possible interpretations of this result, and we comment on experimental implications in heavy ion collisions and atomic systems.
In this Letter we derive the gravity field equations by varying the action for an ultraviolet complete quantum gravity. Then we consider the case of a static source term and we determine an exact black hole solution. As a result we find a regular spacetime geometry: in place of the conventional curvature singularity extreme energy fluctuations of the gravitational field at small length scales provide an effective cosmological constant in a region locally described in terms of a de Sitter space. We show that the new metric coincides with the noncommutative geometry inspired Schwarzschild black hole. Indeed, we show that the ultraviolet complete quantum gravity, generated by ordinary matter is the dual theory of ordinary Einstein gravity coupled to a noncommutative smeared matter. In other words we obtain further insights about that quantum gravity mechanism which improves Einstein gravity in the vicinity of curvature singularities. This corroborates all the existing literature in the physics and phenomenology of noncommutative black holes.
In this paper, we present a family of regular black hole solutions in the presence of charge and angular momentum. We also discuss the related thermodynamics and we comment about the black hole life cycle during the balding and spin down phases. Interestingly the static solution resembles the Ayón-Beato–García spacetime, provided the T-duality scale is redefined in terms of the electric charge, l0→Q. The key factor at the basis of our derivation is the employment of Padmanabhan's propagator to calculate static potentials. Such a propagator encodes string T-duality effects. This means that the regularity of the spacetimes here presented can open a new window on string theory phenomenology.
In this paper we discuss to what extent one can infer details of the interior structure of a black hole based on its horizon. Recalling that black hole thermal properties are connected to the non-classical nature of gravity, we circumvent the restrictions of the no-hair theorem by postulating that the black hole interior is singularity free due to violations of the usual energy conditions. Further these conditions allow one to establish a one-to-one, holographic projection between Planckian areal “bits” on the horizon and “voxels”, representing the gravitational degrees of freedom in the black hole interior. We illustrate the repercussions of this idea by discussing an example of the black hole interior consisting of a de Sitter core postulated to arise from the local graviton quantum vacuum energy. It is shown that the black hole entropy can emerge as the statistical entropy of a gas of voxels.
Physics at its core is an experimental pursuit. If one theory does not agree with experimental results, then the theory is wrong. However, it is becoming harder and harder to directly test some theories of fundamental physics at the high energy/small distance frontier exactly because this frontier is becoming technologically harder to reach. The Large Hadron Collider is getting near the limit of what we can do with present accelerator technology in terms of directly reaching the energy frontier. The motivation for this special issue was to try and collect together ideas and potential approaches to experimentally probe some of our ideas about physics at the high energy/small distance frontier. Some of the papers in this special issue directly deal with the issue of what happens to spacetime at small distance scales. In the paper by A. Aurilia and E. Spallucci a picture of quantum spacetime is given based on the effects of ultrahigh velocity length contractions on the structure of the spacetime. The work of P. Nicolini et al. further pursues the idea that spacetime has a minimal length. The consequences of this minimal length are investigated in terms of the effects it would have on the gravitational collapse of a star to form a black hole. In the article by G. Amelino-Camelia et al. the quantum structure of spacetime is studied through the Fermi LAT data on the Gamma Ray Burst GRB130427A. The article by S. Hossenfelder addressed the question of whether spacetime is fundamentally continuous or discrete and postulates that in the case when spacetime is discrete it might have defects which would have important observational consequences. ...
In this paper, we present the repercussions of Padmanabhan's propagator in electrodynamics. This corresponds to implement T-duality effects in a U(1) gauge theory. By formulating a nonlocal action consistent with the above hypothesis, we derive the profile of static potentials between electric charges via a path integral approach. Interestingly, the Coulomb potential results regularized by a length scale proportional to the parameter (α′)1/2. Accordingly, fields are vanishing at the origin. We also discuss an array of experimental testbeds to expose the above results. It is interesting to observe that T-duality generates an effect of dimensional fractalization, that resembles similar phenomena in fractional electromagnetism. Finally, our results have also been derived with a gauge-invariant method, as a necessary check of consistency for any non-Maxwellian theory.
Fuzziness at the horizon
(2010)
We study the stability of the noncommutative Schwarzschild black hole interior by analysing the propagation of a massless scalar field between the two horizons. We show that the spacetime fuzziness triggered by the field higher momenta can cure the classical exponential blue-shift divergence, suppressing the emergence of infinite energy density in a region nearby the Cauchy horizon.
This paper studies the geometry and the thermodynamics of a holographic screen in the framework of the ultraviolet self-complete quantum gravity. To achieve this goal we construct a new static, neutral, nonrotating black hole metric, whose outer (event) horizon coincides with the surface of the screen. The spacetime admits an extremal configuration corresponding to the minimal holographic screen and having both mass and radius equalling the Planck units. We identify this object as the spacetime fundamental building block, whose interior is physically unaccessible and cannot be probed even during the Hawking evaporation terminal phase. In agreement with the holographic principle, relevant processes take place on the screen surface. The area quantization leads to a discrete mass spectrum. An analysis of the entropy shows that the minimal holographic screen can store only one byte of information, while in the thermodynamic limit the area law is corrected by a logarithmic term.
We present an analysis of the role of the charge within the self-complete quantum gravity paradigm. By studying the classicalization of generic ultraviolet improved charged black hole solutions around the Planck scale, we showed that the charge introduces important differences with respect to the neutral case. First, there exists a family of black hole parameters fulfilling the particle-black hole condition. Second, there is no extremal particle-black hole solution but quasi extremal charged particle-black holes at the best. We showed that the Hawking emission disrupts the condition of particle-black hole. By analyzing the Schwinger pair production mechanism, the charge is quickly shed and the particle-black hole condition can ultimately be restored in a cooling down phase towards a zero temperature configuration, provided non-classical effects are taken into account.