36 research outputs found
Gravity as an emergent phenomenon: a GFT perspective
While the idea of gravity as an emergent phenomenon is an intriguing one,
little is known about concrete implementations that could lead to viable
phenomenology, most of the obstructions being related to the intrinsic
difficulties of formulating genuinely pregeometric theories. In this paper we
present a preliminary discussion of the impact of critical behavior of certain
microscopic models for gravity, based on group field theories, on the dynamics
of the macroscopic regime. The continuum limit is examined in light of some
scaling assumption, and the relevant consequences for low energy effective
theories are discussed, the role of universality, the corrections to scaling,
the emergence of gravitational theories and the nature of their thermodynamical
behavior.Comment: 1+26 page
A note on particle kinematics in Horava-Lifshitz scenarios
In this short note we clarify a link between anisotropic-scaling scenarios
and Finsler spacetimes. Generalizing earlier analysis it is shown that the
kinematics of propagating particles (in the sense of geometrical optics) can be
described in terms of (pseudo-)Finsler structures.Comment: 8 pages. Revised version: some references have been adde
Emergent gravitational dynamics from multi-BEC hydrodynamics?
In this paper, we examine the possibility to implement some form of emergent
Newtonian gravity in a generic multi-component Bose--Einstein condensate.
Parallely to what happens for the emergence of low energy Lorentz invariance,
strong requirements have to be imposed on the underlying condensed matter
model. We will show, within a simplified model, that the presence of a global
symmetry alleviates the problems associated to Lorentz violation, allows the
presence of a long range potential, to which the analogue matter fields (the
quasi-particles) are coupled following a weaker form of equivalence principle.Comment: revtex4, 23 page
Horizon thermodynamics and composite metrics
We examine the conditions under which the thermodynamic behaviour of gravity
can be explained within an emergent gravity scenario, where the metric is
defined as a composite operator. We show that due to the availability of a
boundary of a boundary principle for the quantum effective action,
Clausius-like relations can always be constructed. Hence, any true explanation
of the thermodynamic nature of the metric tensor has to be referred to an
equilibration process, associated to the presence of an H-theorem, possibly
driven by decoherence induced by the pregeometric degrees of freedom, and their
entanglement with the geometric ones.Comment: 11 pages, 1 figur
New coherent states and modified heat equations
We clarify the relations between certain new coherent states for loop quantum
gravity and the analytically continued heat kernel coherent states,
highlighting the underlying general construction, the presence of a modified
heat equation as well as the way in which the properties of the heat kernels
are automatically inherited by these new states.Comment: 7 page
Emergent gravitational dynamics in Bose-Einstein condensates
We discuss a toy model for an emergent non-relativistic gravitational theory.
Within a certain class of Bose-Einstein condensates, it is possible to show
that, in a suitable regime, a modified version of non-relativistic Newtonian
gravity does effectively describes the low energy dynamics of the coupled
system condensate/quasi-particles.Comment: 9 pages. To appear in the Proceedings of the XXV Max Born Symposium,
"The Planck Scale", Wroclaw, Poland, July 200