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We study flat space cosmologies in two dimensions by taking the flat space limit of the Achúcarro-Ortiz model. We unravel a phase transition between hot flat space and flat space cosmologies, and derive a new dilaton-dependent counterterm required for the consistency of the Euclidean partition function. Our results generalize to asymptotically mass-dominated two-dimensional dilaton gravity models, whose thermodynamical properties we discuss. The novel case of asymptotic mass domination is covered neither by the comprehensive discussion of Grumiller and McNees [J. High Energy Phys. 04 (2007) 074] nor by the more recent generalization to dilaton gravity with confining U(1) charges in Grumiller et al. [Phys. Rev. D 90, 044032 (2014)]. [ABSTRACT FROM AUTHOR]

The cosmological constant is treated as a thermodynamical parameter in the framework of two-dimensional dilaton gravity. We find that the cosmological constant behaves as a U(1) charge with a confining potential, and that such potentials require a novel Bom-Infeld boundary term in the action. The free energy and other thermodynamical quantities of interest are derived, from first principles, in a way that is essentially model independent. We discover that there is always a Schottky anomaly in the specific heat and explain its physical origin. Finally, we apply these results to specific examples, like anti-de Sitter-Schwarzschild-Tangherlini black holes, Bañados-Teitelboim-Zanelli black holes and the Jackiw-Teitelboim model. [ABSTRACT FROM AUTHOR]

We provide a well-defined variational principle for three-dimensional flat space Einstein gravity by adding one-half of the Gibbons-Hawking-York boundary term to the bulk action. We check the zero-point function, recovering consistency with thermodynamics of flat space cosmologies. We then apply our result to calculate the one-point functions in flat space Einstein gravity for the vacuum and all flat space cosmologies. The results are compatible with the ones for the zero-mode charges obtained by canonical analysis. [ABSTRACT FROM AUTHOR]

We provide a holographic description of two-dimensional dilaton gravity with anti-de Sitter boundary conditions. We find that the asymptotic symmetry algebra consists of a single copy of the Virasoro algebra with nonvanishing central charge and point out difficulties with the standard canonical treatment. We generalize our results to higher spin theories and thus provide the first examples of two-dimensional higher spin gravity with holographic description. For spin-3 gravity we find that the asymptotic symmetry algebra is a single copy of the W3 algebra. [ABSTRACT FROM AUTHOR]

We consider black holes in an "unsuitable box": a finite cavity coupled to a thermal reservoir at a temperature different than the black hole's Hawking temperature. These black holes are described by metrics that are continuous but not differentiable due to a conical singularity at the horizon. We include them in the Euclidean path integral sum over configurations, and analyze the effect this has on black hole thermodynamics in the canonical ensemble. Black holes with a small deficit (or surplus) angle may have a smaller internal energy or larger density of states than the nearby smooth black hole, but they always have a larger free energy. Furthermore, we find that the ground state of the ensemble never possesses a conical singularity. When the ground state is a black hole, the contributions to the canonical partition function from configurations with a conical singularity are comparable to the contributions from smooth fluctuations of the fields around the black hole background. Our focus is on highly symmetric black holes that can be treated as solutions of two-dimensional dilaton gravity models: examples include Schwarzschild, asymptotically anti-de Sitter, and stringy black holes. [ABSTRACT FROM AUTHOR]

Boson clouds around black holes exhibit interesting physical phenomena through the Penrose process of superradiance, leading to black-hole spin-down. Axionic clouds are of particular interest, since the axion Compton wavelength could be comparable to the Schwarzschild radius, leading to the formation of "gravitational atoms" with a black-hole nucleus. These clouds collapse under certain conditions, leading to a "Bosenova." We model the dynamics of such unstable boson clouds by a simple cellular automaton and show that it exhibits self-organized criticality. Our results suggest that the evolution through the black-hole Regge plane is due to self-organized criticality. [ABSTRACT FROM AUTHOR]

We discuss the classical tests of general relativity in the presence of Rindler acceleration. Among these tests, the perihelion shifts give the tightest constraints and indicate that the Pioneer anomaly cannot be caused by a universal solar system Rindler acceleration. We address potential caveats for massive test objects. Our tightest bound on Rindler acceleration that comes with no caveats is derived from radar echo delay and yields ∣a∣<3??nm/s2. [ABSTRACT FROM AUTHOR]

The quantum null energy condition (QNEC) is a new local energy condition that a general quantum field theory (QFT) is believed to satisfy, relating the classical null energy condition (NEC) to the second functional derivative of the entanglement entropy in the corresponding null direction. We present the first series of explicit computations of QNEC in a strongly coupled QFT, using holography. We consider the vacuum, thermal equilibrium, a homogeneous far-from-equilibrium quench as well as a colliding system that violates NEC. For the vacuum and thermal phase, QNEC is always weaker than NEC. While for the homogeneous quench QNEC is satisfied with a finite gap, we find the interesting result that the colliding system can saturate QNEC, depending on the null direction. [ABSTRACT FROM AUTHOR]

We discuss some aspects of soft hairy black holes and a new kind of "soft hairy cosmologies," including a detailed derivation of the metric formulation, results on flat space, and novel observations concerning the entropy. Remarkably, like in the case with negative cosmological constant, we find that the asymptotic symmetries for locally flat spacetimes with a horizon are governed by infinite copies of the Heisenberg algebra that generate soft hair descendants. It is also shown that the generators of the three-dimensional Bondi-Metzner-Sachs algebra arise from composite operators of the affine u(1) currents through a twisted Sugawara-like construction. We then discuss entropy macroscopically and microscopically and discover that a microscopic formula derived recently for boundary conditions associated with the Korteweg-de Vries hierarchy fits perfectly our results for entropy and ground state energy. We conclude with a comparison to related approaches. [ABSTRACT FROM AUTHOR]

We study chaos in non-Lorentzian field theories, specifically Galilean and Carrollian conformal field theories in two dimensions. In a large central charge limit, we find that the Lyapunov exponent saturates the bound on chaos, conjectured originally for relativistic field theories. We recover the same Lyapunov exponent holographically by a shock-wave calculation in three-dimensional flat space cosmologies, providing further evidence for flat space holography. [ABSTRACT FROM AUTHOR]

We provide the first steps toward a flat space holographic correspondence in two bulk spacetime dimensions. The gravity side is described by a conformally transformed version of the matterless Callan-Giddings-Harvey-Strominger model. The field theory side follows from the complex Sachdev-Ye-Kitaev model in the limit of large specific heat and vanishing compressibility. We derive the boundary action analogous to the Schwarzian as the key link between gravity and field theory sides and show that it coincides with a geometric action discovered recently by one of us [H. R. Afshar, Warped Schwarzian theory, J. High Energy Phys. 02 (2020) 126]. [ABSTRACT FROM AUTHOR]

We discuss a fine-tuning of rather generic 3-dimensional higher-curvature gravity actions that leads to gauge symmetry enhancement at the linearized level via partial masslessness. Requiring this gauge symmetry to be present also nonlinearly reduces such actions to conformai Chern-Simons gravity. We perform a canonical analysis of this theory and construct the gauge generators and associated charges. We provide and classify admissible boundary conditions. The boundary conditions on the conformai equivalence class of the metric render one chirality of the partially massless Weyl gravitons normalizable and the remaining one non-normalizable. There are three choices--trivial, fixed, or free--for the Weyl factors of the bulk metric and of the boundary metric. This proliferation of boundary conditions leads to various physically distinct scenarios of holography that we study in detail, extending considerably the discussion initiated in Ref. [1], In particular, the dual CFT may contain an additional scalar field with or without background charge, depending on the choices above. [ABSTRACT FROM AUTHOR]

We show that conformal Chern-Simons gravity in three dimensions has various holographic descriptions. They depend on the boundary conditions on the conformal equivalence class and the Weyl factor, even when the former is restricted to asymptotic anti--de Sitter behavior. For constant or fixed Weyl factor our results agree with a suitable scaling limit of topologically massive gravity results. For varying Weyl factor we find an enhancement of the asymptotic symmetry group, the details of which depend on certain choices. We focus on a particular example where an affine û(1) algebra related to holomorphic Weyl rescalings shifts one of the central charges by 1. The Weyl factor then behaves as a free chiral boson in the dual conformal field theory. [ABSTRACT FROM AUTHOR]