Fri - 07/22/22

There is no new related paper today

There is no new related paper today

  1. [2207.10339] - Tunneling Analysis of Regular Black Holes with Cosmic Strings-Like Solution in Newman-Janis Algorithm - Riasat Ali, Rimsha Babar, Muhammad Asgher, Xia Tie-Cheng

  2. [2207.10467] - Evaporation of a Kerr-black-bounce by emission of scalar particles - Marco Calzá

  3. [2207.10115] - Line of Fixed Points in Gross-Neveu Theories - Charlie Cresswell-Hogg, Daniel F. Litim

  4. [2207.10598] - Integrable crosscap states in $\mathfrak{gl}(N)$ spin chains - Tamas Gombor

  5. [2207.10618] - Frontiers of Quantum Gravity: shared challenges, converging directions - Jan de Boer, Bianca Dittrich, Astrid Eichhorn, Steven B. Giddings, Steffen Gielen, Stefano Liberati, Etera R. Livine, Daniele Oriti, Kyriakos Papadodimas, Antonio D. Pereira, Mairi Sakellariadou, Sumati Surya, Herman Verlinde

  6. [2207.10636] - Solving Scattering in N=4 Super-Yang-Mills Theory - Nima Arkani-Hamed, Lance J. Dixon, Andrew J. McLeod, Marcus Spradlin, Jaroslav Trnka, Anastasia Volovich

Thu - 07/21/22

There is no new related paper today

There is no new related paper today

  1. [2207.09817] - The Asymptotically Safe Standard Model: From quantum gravity to dynamical chiral symmetry breaking - Álvaro Pastor-Gutiérrez, Jan M. Pawlowski, Manuel Reichert

Wed - 07/20/22

There is no new related paper today

There is no new related paper today

  1. [2207.08864] - Stable Rotating Regular Black Holes - Edgardo Franzin, Stefano Liberati, Jacopo Mazza, Vania Vellucci

  2. [2207.08846] - Localization vs holography in $4d$ $\mathcal{N}=2$ quiver theories - M. Billo, M. Frau, A. Lerda, A. Pini, P. Vallarino

Tue - 07/19/22

Non-degenerate metrics, hypersurface deformation algebra, non-anomalous representations and density weights in quantum gravity

  • Authors: T. Thiemann
  • Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
  • Arxiv link: https://arxiv.org/abs/2207.08299
  • Abstract A basic assumption in classical GR is that the metric field is nowhere degenerate in spacetime. In particular the induced metric on Cauchy surfaces must be nowhere degenerate. It is only under this assumption that one can derive the hypersurace deformation algebra between the initial value constraints which is absolutely transparent from the fact that the {\it inverse} of the induced metric is needed to close the algebra. This statement is independent of the density weight that one may want to equip the spatial metric with. Accordingly, the very definition of a non-anomalous representation of the hypersurface defomation algebra in quantum gravity has to address the issue of non-degenracy of the induced metric that is needed in the classical theory. In the Hilbert space representation employed in Loop Quantum Gravity (LQG) most emphasis has been layed to define an inverse metric operator on the dense domain of spin network states although they represent induced quantum geometries which are degenerate almost everywhere. It is no surprise that demonstration of closure of the constraint algebra on this domain meets difficulties because it is a sector of the quantum theory which is classically forbidden and which lies outside the domain of definition of the classical hypersurface deformation algebra. Various suggestions for addressing the issue such as non-standard operator topologies, dual spaces (habitats) and density weights have been propposed to address this issue with respect to the quantum dynamics of LQG. In this article we summarise these developments and argue that insisting on a dense domain of non-degenerate states within the LQG representation may provide a natural resolution of the issue thereby possibly avoiding the above mentioned non-standard constructions.

An open scattering model in polymerized quantum mechanics

  • Authors: Kristina Giesel, Michael Kobler
  • Subjects: General Relativity and Quantum Cosmology (gr-qc); Quantum Physics (quant-ph)
  • Arxiv link: https://arxiv.org/abs/2207.08749
  • Abstract We derive a quantum master equation in the context of a polymerized open quantum mechanical system for the scattering of a Brownian particle in an ideal gas environment. The model is formulated in a top-down approach by choosing a Hamiltonian with a coupling between the system and environment that is generally associated with spatial decoherence. We extend the existing work on such models by using a non-standard representation of the canonical commutation relations, inspired by the quantization procedure applied in loop quantum gravity, which yields a model in which position operators are replaced by holonomies. The derivation of the master equation in a top-down approach opens up the possibility to investigate in detail whether the assumptions, usually used in such models in order to obtain a tractable form of the dissipator, hold also in the polymerized case or whether they need to be dropped or modified. Furthermore, we discuss some physical properties of the master equation associated to effective equations for the expectation values of the fundamental operators and compare our results to the already existing models of collisional decoherence.

Exact quantisation of U(1)$^3$ quantum gravity via exponentiation of the hypersurface deformation algebroid

  • Authors: T. Thiemann
  • Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
  • Arxiv link: https://arxiv.org/abs/2207.08302
  • Abstract The U(1)$^3$ model for 3+1 Euclidian signature general relativity is an interacting, generally covariant field theory with two physical polarisations that shares many features of Lorentzian general relativity. In particular, it displays a non-trivial realisation of the hypersurface deformation algebroid with non-trivial, i.e. phase space dependent structure functions rather than structure constants. In this paper we show that the model admits {\it an exact quantisation}. The quantisation rests on the observation that for this model and in the chosen representation of the canonical commutation relations the density unity hypersurface algebra {\it can be exponentiated on non-degenerate states}. These are states that represent a non-degenerate quantum metric and from a classical perspective are the relevant states on which the hypersurface algebra is representable. The representation of the algebra is exact, with no ambiguities involved and anomaly free. The quantum constraints can be exactly solved using {\it groupoid averaging} and the solutions admit a Hilbert space structure that agrees with the quantisation of a recently found reduced phase space formulation. Using the also recently found covariant action for that model, we start a path integral or spin foam formulation which, due to the Abelian character of the gauge group, is much simpler than for Lorentzian signature general relativity and provides an ideal testing ground for general spin foam models.

Renormalisation, wavelets and the Dirichlet-Shannon kernels

  • Authors: T. Thiemann
  • Subjects: [‘hep-th’, ‘gr-qc’, ‘hep-lat’]
  • Arxiv link: http://arxiv.org/abs/2207.08294v1
  • Abstract In constructive quantum field theory (CQFT) it is customary to first regularise the theory at finite UV and IR cut-off. Then one first removes the UV cutoff using renormalisation techniques applied to families of CQFT’s labelled by finite UV resolutions and then takes the thermodynamic limit. Alternatively, one may try to work directly without IR cut-off. More recently, wavelets have been proposed to define the renormalisation flow of CQFT’s which is natural as they come accompanied with a multi-resolution analysis (MRA). However, wavelets so far have been mostly studied in the non-compact case. Practically useful wavelets that display compact support and some degree of smoothness can be constructed on the real line using Fourier space techniques but explicit formulae as functions of position are rarely available. Compactly supported wavelets can be periodised by summing over period translates keeping orthogonality properties but still yield to rather complicated expressions which generically lose their smoothness and position locality properties. It transpires that a direct approach to wavelets in the compact case is desirable. In this contribution we show that the Dirichlet-Shannon kernels serve as a natural scaling function to define generalised orthonormal wavelet bases on tori or copies of real lines respectively. These generalised wavelets are smooth, are simple explicitly computable functions, display quasi-local properties close to the Haar wavelet and have compact momentum supprt. Accordingly they have a built-in cut-off both in position and momentum, making them very useful for renormalisation applications.

Hamiltonian Renormalisation VII: Free fermions and doubler free kernels

  • Authors: T. Thiemann
  • Subjects: [‘hep-th’, ‘gr-qc’, ‘hep-lat’]
  • Arxiv link: http://arxiv.org/abs/2207.08291v1
  • Abstract The Hamiltonian renormalisation programme motivated by constructive QFT and Osterwalder-Schrader reconstruction which was recently launched for bosonic field theories is extended to fermions. As fermion quantisation is not in terms of measures, the scheme has to be mildly modified accordingly. We exemplify the scheme for free fermions both for compact and non-compact spatial topologies respectively (i.e. with and without IR cut-off) and demonstrate that the convenient Dirichlet or Shannon coarse graining kernels recently advertised in a companion paper lead to a manifestly doubler free flow.

Hamiltonian renormalisation VI: Parametrised field theory on the cylinder

  • Authors: T. Thiemann, E. -A. Zwicknagel
  • Subjects: [‘gr-qc’, ‘hep-lat’, ‘hep-th’]
  • Arxiv link: http://arxiv.org/abs/2207.08290v1
  • Abstract Hamiltonian Renormalisation, as defined within this series of works, was derived from covariant Wilson renormalisation via Osterwalder-Schrader reconstruction. As such it directly applies to QFT with a true (physical) Hamiltonian bounded from below. The validity of the scheme was positively tested for free QFT in any dimension with or without Abelian gauge symmetries of Yang-Mills type. The aim of this Hamiltonian renormalisation scheme is to remove quantisation ambiguities of Hamiltonians in interacting QFT that remain even after UV and IR regulators are removed as it happens in highly non-linear QFT such as quantum gravity. While not derived for that case, the renormalisation flow formulae can without change also be applied to QFT without a single true Hamiltonian but rather an infinite number of Hamiltonian constraints. Then a central question is how the constraint algebra reacts to the renormalisation flow. This question should ultimately be addressed in quantum gravity. Before one considers this interacting, constrained QFT it is well motivated to consider a free, constrained QFT where the fixed point is explicitly known. In this paper we therefore address the case of parametrised field theory for which the quantum constraint algebra coincides simultaneously with the hypersurface deformation algebra of quantum gravity (or any other generally covariant theory) and the Virasoro algebra of free, closed, bosonic string theory or other CFT to which the results of this paper apply verbatim. The central result of our investigation is that finite resolution (discretised) constraint algebras {\it must not close} and that anomaly freeness of the continuum algebra is encoded in the convergence behaviour of the renormalisation flow.

There is no new related paper today

  1. [2207.07652] - Bouncing cosmological model with general relativistic hydrodynamics in extended gravity - A.Y. Shaikh, Sankarsan Tarai, S.K. Tripathy, B.Mishra

  2. [2207.07667] - Massive Neutron Stars and White Dwarfs as Noncommutative Fuzzy Spheres - Surajit Kalita (UCT), Banibrata Mukhopadhyay (IISc)

  3. [2207.08471] - Relativistic deformed kinematics: from flat to curved spacetimes - J.J. Relancio

Mon - 07/18/22

There is no new related paper today

There is no new related paper today

  1. [2207.07312] - Schrödinger symmetry in cosmology and black hole mechanics - Jibril Ben Achour, Etera R. Livine, Daniele Oriti, Goffredo Piani

  2. [2207.07529] - Astrophysical observables for regular black holes with sub-Planckian curvature - Wei Zeng, Yi Ling, Qing-Quan Jiang

  3. [2207.07138] - Normalization of D instanton amplitudes in two dimensional type 0B string theory - Joydeep Chakravarty, Ashoke Sen

  4. [2207.07507] - Higher-spin gravity’s “string”: new gauge and proof of holographic duality for the linearized Didenko-Vasiliev solution - Vyacheslav Lysov, Yasha Neiman

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