118515677
Higher spin black hole entropy in three dimensions
A bstractA generic formula for the entropy of three-dimensional black holes endowed with a spin-3 field is found, which depends on the horizon area A and its spin-3 analogue $ \varphi_{+}^{{{1 \left/ {3} \right.}}} $, given by the reparametrization invariant integral of the induced spin-3 field at the spacelike section of the horizon. From this result it can be shown that the absolute value of $ {\varphi_{+}} $ has to be bounded from above according to $ {{\left| {{\varphi_{+}}} \right|}^{{{1 \left/ {3} \right.}}}}\leq {A \left/ {{\sqrt{3}}} \right.} $. The entropy formula is constructed by requiring the first law of thermodynamics to be fulfilled in terms of the global charges obtained through the canonical formalism. For the static case, in the weak spin-3 field limit, our expression for the entropy reduces to the result found by Campoleoni, Fredenhagen, Pfenninger and Theisen, which has been recently obtained through a different approach.
124142447
Higher Spin Black Holes
We review some relevant results in the context of higher spin black holes in three-dimensional spacetimes, focusing on their asymptotic behaviour and thermodynamic properties. For simplicity, we mainly discuss the case of gravity nonminimally coupled to spin-three fields, being nonperturbatively described by a Chern–Simons theory of two independent \(\mathit{sl}\left (3, \mathbb{R}\right )\) gauge fields. Since the analysis is particularly transparent in the Hamiltonian formalism, we provide a concise discussion of their basic aspects in this context; and as a warming up exercise, we briefly analyze the asymptotic behaviour of pure gravity, as well as the BTZ black hole and its thermodynamics, exclusively in terms of gauge fields. The discussion is then extended to the case of black holes endowed with higher spin fields, briefly signaling the agreements and discrepancies found through different approaches. We conclude explaining how the puzzles become resolved once the fall off of the fields is precisely specified and extended to include chemical potentials, in a way that it is compatible with the asymptotic symmetries. Hence, the global charges become completely identified in an unambiguous way, so that different sets of asymptotic conditions turn out to contain inequivalent classes of black hole solutions being characterized by a different set of global charges.
6843889
Finiteness of a spinfoam model for Euclidean quantum general relativity
Abstract We prove that a certain spinfoam model for Euclidean quantum general relativity, recently defined, is finite: all its all Feynman diagrams converge. The model is a variant of the Barrett–Crane model, and is defined in terms of a field theory over SO(4)×SO(4)×SO(4)×SO(4) .
118853593
The theta parameter in loop quantum gravity: effects on quantum geometry and black hole entropy
The precise analog of the theta-quantization ambiguity of Yang-Mills theory exists for the real SU(2) connection formulation of general relativity. As in the former case theta labels representations of large gauge transformations, which are super-selection sectors in loop quantum gravity. We show that unless theta=0, the (kinematical) geometric operators such as area and volume are not well defined on spin network states. More precisely the intersection of their domain with the dense set Cyl in the kinematical Hilbert space H of loop quantum gravity is empty. The absence of a well defined notion of area operator acting on spin network states seems at first in conflict with the expected finite black hole entropy. However, we show that the black hole (isolated) horizon area--which in contrast to kinematical area is a (Dirac) physical observable--is indeed well defined, and quantized so that the black hole entropy is proportional to the area. The effect of theta is negligible in the semiclassical limit where proportionality to area holds.
33010210
Spin foam model for Lorentzian general relativity
We present a spin foam formulation of Lorentzian quantum general relativity. The theory is based on a simple generalization of a Euclidean model defined in terms of a field theory over a group. Its vertex amplitude turns out to be the one recently introduced by Barrett and Crane. As in the case of its Euclidean relatives, the model fully implements the desired sum over 2-complexes which encodes the local degrees of freedom of the theory.
118468497
3+1 spinfoam model of quantum gravity with spacelike and timelike components
We present a spin foam formulation of Lorentzian quantum general relativity. The theory is based on a simple generalization of a Euclidean model defined in terms of a field theory over a group. The model is an extension of a recently introduced Lorentzian model, in which both timelike and spacelike components are included. The spin foams in the model, corresponding to quantized 4-geometries, carry a natural nonperturbative local causal structure induced by the geometry of the algebra of the internal gauge $[\mathrm{sl}(2,C)].$ Amplitudes can be expressed as integrals over the spacelike unit vectors hyperboloid in Minkowski space, or the imaginary Lobachevskian space.
115931245
Rare Decays with Missing Energy at SuperB
The study of rare B-decays at SuperB provides unique opportunities to understand the Standard Model and to constrain new physics. It is discussed the new physics potential of the B -> K\nu\nu and B -> K^*\nu\nu system from the proposed SuperB experiment with 75ab-1 of data (5 nominal years of data taking).