16,519 research outputs found
Quasiparticle picture from the Bekenstein bound
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.Comment: 11 pages, 1 figure, Corfu Summer Institute 2017 'School and Workshops
on Elementary Particle Physics and Gravity', 2-28 September 2017, Corfu,
Greec
Emergent Dark Matter in Late Time Universe on Holographic Screen
We discuss a scenario that the dark matter in late time universe emerges as
part of the holographic stress-energy tensor on the hypersurface in higher
dimensional flat spacetime. Firstly we construct a toy model with a de Sitter
hypersurface as the holographic screen in the flat bulk. After adding the
baryonic matter on the screen, we assume that both of the dark matter and dark
energy can be described by the Brown-York stress-energy tensor. From the
Hamiltonian constraint equation in the flat bulk, we find an interesting
relation between the dark matter and baryonic matter's energy density
parameters, by comparing with the Lambda cold dark matter parameterization. We
further compare this holographic embedding of emergent dark matter with
traditional braneworld scenario and present an alternative interpretation as
the holographic universe. It can be reduced to our toy constraint in the late
time universe, with the new parameterization of the Friedmann equation. We also
comment on the possible connection with Verlinde's emergent gravity, where the
dark matter is treated as the elastic response of the baryonic matter on the de
Sitter spacetime background. We show that from the holographic de Sitter model
with elasticity, the Tully-Fisher relation and the dark matter distribution in
the galaxy scale can be derived.Comment: 28 pages, 2 figures; Matches published version and we thank the
referees for many insightful comments; v3: typos in the Friedmann equations
are fixe
Cosmological consequences in the framework of generalized Rastall theory of gravity
The paper deals with generalized Rastall theory of gravity and its
cosmological consequences in the background of homogeneous and isotropic flat
FLRW model with perfect fluid as the matter context. The model shows a non
singular era (emergent scenario) at the early phase of expansion for a
particular choice of the Rastall parameter. Also the model finds to be
equivalent to the particle creation mechanism in Einstein gravity in the
framework of non-equilibrium thermodynamics. Universal thermodynamics is
briefly presented and it is found that the entropy function in Rastall theory
is the usual Bekenstein entropy and there is no correction to it. Finally, a
complete cosmic history starting from inflation to late time acceleration is
presented for suitable choices of the Rastall parameter
Structural Aspects Of Gravitational Dynamics And The Emergent Perspective Of Gravity
I describe several conceptual aspects of a particular paradigm which treats
the field equations of gravity as emergent. These aspects are related to the
features of classical gravitational theories which defy explanation within the
conventional perspective. The alternative interpretation throws light on these
features and could provide better insights into possible description of quantum
structure of spacetime. This review complements the discussion in
arXiv:1207.0505, which describes space itself as emergent in the cosmological
context.Comment: Updated version of talks given at: (a) Sixth International School on
Field Theory and Gravitation - 2012, Petropolis, Brazil; (b) Colloquium at
Institute of Astrophysics, Paris, 2012 and (c) Discussion meeting on String
Theory, International Centre for Theoretical Sciences, Bangalore, 201
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