Conference Presentations by Giovanni Acquaviva
We provide general arguments regarding the connection between low-energy theories (gravity and qu... more We provide general arguments regarding the connection between low-energy theories (gravity and quantum field theory) and a hypothetical fundamental theory of quantum gravity, under the assumptions of (i) validity of the holographic bound and (ii) preservation of unitary evolution at the level of the fundamental theory. In particular, the appeal to the holographic bound imposed on generic physical systems by the Bekenstein-Hawking entropy implies that both classical geometry and quantum fields propagating on it should be regarded as phenomena emergent from the dynamics of the fundamental theory. The reshuffling of the fundamental degrees of freedom during the unitary evolution then leads to an entanglement between geometry and quantum fields. The consequences of such scenario are considered in the context of black hole evaporation and the related information-loss issue: we provide a simplistic toy model in which an average loss of information is obtained as a consequence of the geometry-field entanglement.
Dissipative features of dark matter affect its clustering properties and could lead to observable... more Dissipative features of dark matter affect its clustering properties and could lead to observable consequences for the evolution of large–scale structure. We analyse the evolution of cold dark matter density perturbations allowing for the possibility of bulk viscous pressure in a causal dissipative theory. Our analysis employs a Newtonian approximation for cosmological dynamics and the transport properties of bulk viscosity are described by the Israel–Stewart theory. We obtain a third order evolution equation for density perturbations. For some parameter values the density contrast can be suppressed compared to results obtained in the ΛCDM scenario. For other values causal bulk viscous dark matter can exhibit an enhancement of clustering.
Thermal aspects in curved metrics
In this paper we describe two approaches that allow to calculate some thermal features as perceiv... more In this paper we describe two approaches that allow to calculate some thermal features as perceived by different observers in curved spacetimes: the tunnelling method and the Unruh-DeWitt detector. The tunnelling phenomenon is a semi-classical approach to the issue of Hawking radiation and allows a straightforward calculation of the horizon temperature in a plethora of scenarios; the Unruh-DeWitt model relies instead on a quantum field-theoretical approach and (whenever possible) gives a more exact answer in terms of transition rates between energy levels of an idealized detector.
Quantum fields in gravity
We give a brief description of some compelling connections between general relativity and thermod... more We give a brief description of some compelling connections between general relativity and thermodynamics through i) the semi-classical tunnelling method(s) and ii) the field-theoretical modelling of Unruh-DeWitt detectors. In both approaches it is possible to interpret some quantities in a thermodynamical frame.
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Conference Presentations by Giovanni Acquaviva