scholarly journals Black hole microstates from the worldsheet

2021 ◽  
Vol 2021 (8) ◽  
Author(s):  
Davide Bufalini ◽  
Sergio Iguri ◽  
Nicolas Kovensky ◽  
David Turton
Keyword(s):  
Black Hole ◽  
Bound States ◽  
A Priori ◽  
Length Scale ◽  
Geometrical Analysis ◽  
Closed Timelike Curves ◽  
General Family ◽  
Complete Set ◽  
Coset Models

Abstract Recently an exact worldsheet description of strings propagating in certain black hole microstate geometries was constructed in terms of null-gauged WZW models. In this paper we consider a family of such coset models, in which the currents being gauged are specified by a set of parameters that a priori take arbitrary values. We show that consistency of the spectrum of the worldsheet CFT implies a set of quantisation conditions and parity restrictions on the gauging parameters. We also derive these constraints from an independent geometrical analysis of smoothness, absence of horizons and absence of closed timelike curves. This allows us to prove that the complete set of consistent backgrounds in this class of models is precisely the general family of (NS5-decoupled) non-BPS solutions known as the JMaRT solutions, together with their various (BPS and non-BPS) limits. We clarify several aspects of these backgrounds by expressing their six-dimensional solutions explicitly in terms of five non-negative integers and a single length-scale. Finally we study non-trivial two-charge limits, and exhibit a novel set of non-BPS supergravity solutions describing bound states of NS5 branes carrying momentum charge.

scholarly journals Black hole superradiance as a probe of ultra-light new particles

2016 ◽  
Vol 12 (S324) ◽  
pp. 273-278
Author(s):  
Robert Lasenby
Keyword(s):  
Beyond Standard Model ◽  
Black Holes ◽  
Black Hole ◽  
Standard Model ◽  
Gravitational Wave ◽  
Exponential Growth ◽  
Gravitational Radiation ◽  
Bound States ◽  
Penrose Process ◽  
Energy And Momentum

AbstractBosonic fields around a spinning black hole can be amplified via ‘superradiance’, a wave analogue of the Penrose process, which extracts energy and momentum from the black hole. For hypothetical ultra-light bosons, with Compton wavelengths on ≳ km scales, such a process can lead to the exponential growth of gravitationally bound states around astrophysical Kerr black holes. If such particles exist, as predicted in many theories of beyond Standard Model physics, then these bosonic clouds give rise to a number of potentially-observable signals. Among the most promising are monochromatic gravitational radiation signals which could be detected at Advanced LIGO and future gravitational wave observatories.

scholarly journals BLACK HOLE PHYSICS, CONFINING SOLUTIONS OF SU(3)-YANG– MILLS EQUATIONS AND RELATIVISTIC MODELS OF MESONS

2001 ◽  
Vol 16 (09) ◽  
pp. 557-569 ◽  
Author(s):  
YU. P. GONCHAROV
Keyword(s):  
Black Hole ◽  
Dirac Equation ◽  
Exact Solutions ◽  
Bound States ◽  
Black Hole Physics ◽  
Approximate Solutions ◽  
Yang Mills ◽  
Minkowski Space Time ◽  
Relativistic Models ◽  
Relativistic Bound States

The black hole physics techniques and results are applied to find a set of exact solutions of the SU(3)-Yang–Mills equations in Minkowski space–time in the Lorentz gauge. All the solutions contain only the Coulomb-like or linear in r components of SU(3)-connection. This allows one to obtain some possible exact and approximate solutions of the corresponding Dirac equation that can describe the relativistic bound states. Possible application to the relativistic models of mesons is also outlined.

scholarly journals Impact of Covariance Localization on Ensemble Estimation of Surface Downwelling Longwave and Shortwave Radiation Fluxes

2012 ◽  
Vol 13 (4) ◽  
pp. 1301-1316
Author(s):  
B. A. Forman ◽  
S. A. Margulis
Keyword(s):  
Land Surface ◽  
A Priori ◽  
Radiative Flux ◽  
Spatiotemporal Variability ◽  
Shortwave Radiation ◽  
Length Scale ◽  
Sources Of Information ◽  
Modest Improvement ◽  
Radiation Fluxes ◽  
Flux Estimation

Abstract Accurate estimates of terrestrial hydrologic states and fluxes are, in large part, dependent on accurate estimates of the spatiotemporal variability and uncertainty of land surface forcings, including downwelling longwave (LW) and shortwave (SW) fluxes. However, such characterization of land surface forcings does not always receive proper attention. This study attempts to better estimate LW and SW fluxes, including their uncertainties, by merging different sources of information while considering horizontal error correlations via implementation of a 2D conditioning procedure within a Bayesian framework. A total of 25 experiments were performed utilizing four different, readily available downwelling radiation products. The localized region of space used to constrain horizontal error correlations was defined using an influence length, , specified a priori. Quantitative comparisons are made against an independent, ground-based observational network. In general, results suggest moderate improvement in cloudy-sky LW fluxes and modest improvement in clear-sky SW fluxes during certain times of the year when using the 2D framework relative to a more traditional 1D framework, but only up to a certain influence length scale. Beyond this length scale the flux estimates were typically degraded because of the introduction of spurious correlations. The influence length scale that yielded the greatest improvement in LW radiative flux estimation during cloudy-sky conditions, in general, increased with increasing cloud cover. These findings have implications for improving downwelling radiative flux estimation and further enhancing existing Land Data Assimilation System (LDAS) frameworks.

scholarly journals DUALITIES, COMPOSITENESS AND SPACE–TIME STRUCTURE OF 4D EXTREME STRINGY BLACK HOLES

1999 ◽  
Vol 14 (07) ◽  
pp. 1015-1034 ◽  
Author(s):  
MARIANO CADONI
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
String Theory ◽  
Bound States ◽  
Bound State ◽  
Space Time ◽  
Naked Singularities ◽  
Heterotic String Theory ◽  
Space Time Structure ◽  
Black Hole Solutions

We study the BPS black hole solutions of the (truncated) action for heterotic string theory compactified on a six-torus. The O (3,Z) duality symmetry of the theory, together with the bound state interpretation of extreme black holes, is used to generate the whole spectrum of the solutions. The corresponding space–time structures, written in terms of the string metric, are analyzed in detail. In particular, we show that only the elementary solutions present naked singularities. The bound states have either null singularities (electric solutions) or are regular (magnetic or dyonic solutions) with near-horizon geometries given by the product of two 2d spaces of constant curvature. The behavior of some of these solutions as supersymmetric attractors is discussed. We also show that our approach is very useful to understand some of the puzzling features of charged black hole solutions in string theory.

scholarly journals AN INTRODUCTION TO LOCAL BLACK HOLE HORIZONS IN THE 3+1 APPROACH TO GENERAL RELATIVITY

2012 ◽  
Vol 07 ◽  
pp. 31-66
Author(s):  
JOSÉ LUIS JARAMILLO
Keyword(s):  
Black Hole ◽  
First Principles ◽  
Strong Field ◽  
A Priori ◽  
Einstein Equations ◽  
A Posteriori ◽  
Initial Value ◽  
Black Hole Spacetimes ◽  
Local Horizon ◽  
Trapping Horizons

We present an introduction to dynamical trapping horizons as quasi-local models for black hole horizons, from the perspective of an Initial Value Problem approach to the construction of generic black hole spacetimes. We focus on the geometric and structural properties of these horizons aiming, as a main application, at the numerical evolution and analysis of black hole spacetimes in astrophysical scenarios. In this setting, we discuss their dual role as an a priori ingredient in certain formulations of Einstein equations and as an a posteriori tool for the diagnosis of dynamical black hole spacetimes. Complementary to the first-principles discussion of quasi-local horizon physics, we place an emphasis on the rigidity properties of these hypersurfaces and their role as privileged geometric probes into near-horizon strong-field spacetime dynamics.

Stationary bound states of massless scalar fields around black holes and black hole analogues

2015 ◽  
Vol 24 (09) ◽  
pp. 1542018 ◽  
Author(s):  
Carolina L. Benone ◽  
Luís C. B. Crispino ◽  
Carlos A. R. Herdeiro ◽  
Eugen Radu
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Spatial Distribution ◽  
Scalar Field ◽  
Bound States ◽  
Neumann Boundary ◽  
Mass Term ◽  
Scalar Fields ◽  
Massless Scalar ◽  
Field System

We discuss stationary bound states, a.k.a. clouds, for a massless test scalar field around Kerr black holes (BHs) and spinning acoustic BH analogues. In view of the absence of a mass term, the trapping is achieved via enclosing the BH — scalar field system in a cavity and imposing Dirichlet or Neumann boundary conditions. We discuss the variation of these bounds states with the discrete parameters that label them, as well as their spatial distribution, complementing results in our previous work [C. L. Benone, L. C. B. Crispino, C. Herdeiro and E. Radu, Phys. Rev. D91 (2015) 104038].

scholarly journals BOUNDARY BOUND STATES IN AFFINE TODA FIELD THEORY

1995 ◽  
Vol 10 (05) ◽  
pp. 739-751 ◽  
Author(s):  
ANDREAS FRING ◽  
ROLAND KÖBERLE
Keyword(s):  
Field Theory ◽  
Bound States ◽  
Dynkin Diagram ◽  
Binding Energies ◽  
Field Theories ◽  
Complete Set ◽  
Reflecting Boundaries ◽  
Toda Field Theory

We demonstrate that the generalization of the Coleman–Thun mechanism may be applied to the situation where one considers scattering processes in 1 + 1 dimensions in the presence of reflecting boundaries. For affine Toda field theories we find that the binding energies of the bound states are always half the sum over a set of masses having the same color with respect to the bicoloration of the Dynkin diagram. For the case of E6 affine Toda field theory we compute explicitly the spectrum of all higher boundary bound states. The complete set of states constitutes a closed bootstrap.

scholarly journals Semi-classical analysis of the string theory cigar

2021 ◽  
Vol 2021 (12) ◽  
Author(s):  
Daniel Louis Jafferis ◽  
Elliot Schneider
Keyword(s):  
Black Hole ◽  
Reflection Coefficient ◽  
Saddle Point ◽  
Classical Limit ◽  
Bound States ◽  
Functional Integral ◽  
Target Space ◽  
Model Description ◽  
Weakly Coupled ◽  
Linear Dilaton

Abstract We study the semi-classical limit of the reflection coefficient for the SL(2, ℝ)k/U(1) CFT. For large k, the CFT describes a string in a Euclidean black hole of 2-dimensional dilaton-gravity, whose target space is a cigar with an asymptotically linear dilaton. This sigma-model description is weakly coupled in the large k limit, and we investigate the saddle-point expansion of the functional integral that computes the reflection coefficient. As in the semi-classical limit of Liouville CFT studied in [1], we find that one must complexify the functional integral and sum over complex saddles to reproduce the limit of the exact reflection coefficient. Unlike Liouville, the SL(2, ℝ)k/U(1) CFT admits bound states that manifest as poles of the reflection coefficient. To reproduce them in the semi-classical limit, we find that one must sum over configurations that hit the black hole singularity, but nevertheless contribute to the saddle-point expansion with finite action.

scholarly journals Majorana/Andreev crossover and the fate of the topological phase transition in inhomogeneous nanowires

2021 ◽  
Author(s):  
Pasquale Marra ◽  
Angela Nigro
Keyword(s):  
Bound States ◽  
Transition Probabilities ◽  
Topological Invariants ◽  
Length Scale ◽  
Topological Phase ◽  
Andreev Bound States ◽  
Majorana Bound States ◽  
Topological Phase Transition ◽  
Majorana Modes ◽  
Global And Local

Abstract Majorana bound states (MBS) and Andreev bound states (ABS) in realistic Majorana nanowires setups have similar experimental signatures which make them hard to distinguishing one from the other. Here, we characterize the continuous Majorana/Andreev crossover interpolating between fully-separated, partially-separated, and fully-overlapping Majorana modes, in terms of global and local topological invariants, fermion parity, quasiparticle densities, Majorana pseudospin and spin polarizations, density overlaps and transition probabilities between opposite Majorana components. We found that in inhomogeneous wires, the transition between fully-overlapping trivial ABS and nontrivial MBS does not necessarily mandate the closing of the bulk gap of quasiparticle excitations, but a simple parity crossing of partially-separated Majorana modes (ps-MM) from trivial to nontrivial regimes. We demonstrate that fully-separated and fully-overlapping Majorana modes correspond to the two limiting cases at the opposite sides of a continuous crossover: the only distinction between the two can be obtained by estimating the degree of separations of the Majorana components. This result does not contradict the bulk-edge correspondence: Indeed, the field inhomogeneities driving the Majorana/Andreev crossover have a length scale comparable with the nanowire length, and therefore correspond to a nonlocal perturbation which breaks the topological protection of the MBS.

scholarly journals On the verification of climate reconstructions

2007 ◽  
Vol 3 (3) ◽  
pp. 397-409 ◽  
Author(s):  
G. Bürger
Keyword(s):  
A Priori ◽  
Inverse Regression ◽  
Limited Sample ◽  
Climate Reconstructions ◽  
Skill Scores ◽  
Calibration Sets ◽  
Significance Levels ◽  
Complete Set ◽  
Almost All ◽  
Representative Samples

Abstract. The skill of proxy-based reconstructions of Northern hemisphere temperature is reassessed. Using an almost complete set of proxy and instrumental data of the past 130 years a multi-crossvalidation is conducted of a number of statistical methods, producing a distribution of verification skill scores. Among the methods are multiple regression, multiple inverse regression, total least squares, RegEM, all considered with and without variance matching. For all of them the scores show considerable variation, but previous estimates, such as a 50% reduction of error (RE), appear as outliers and more realistic estimates vary about 25%. It is shown that the overestimation of skill is possible in the presence of strong persistence (trends). In that case, the classical "early" or "late" calibration sets are not representative for the intended (instrumental, millennial) domain. As a consequence, RE scores are generally inflated, and the proxy predictions are easily outperformed by stochastic, a priori skill-less predictions. To obtain robust significance levels the multi-crossvalidation is repeated using stochastic predictors. Comparing the score distributions it turns out that the proxies perform significantly better for almost all methods. The scores of the stochastic predictors do not vanish, nonetheless, with an estimated 10% of spurious skill based on representative samples. I argue that this residual score is due to the limited sample size of 130 years, where the memory of the processes degrades the independence of calibration and validation sets. It is likely that proxy prediction scores are similarly inflated and have to be downgraded further, leading to a final overall skill that for the best methods lies around 20%. The consequences of the limited verification skill for millennial reconstructions is briefly discussed.

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