Black hole thermodynamics from Euclidean horizon constraints

To explain black hole thermodynamics in quantum gravity, one must introduce constraints to ensure that a black hole is actually present. I show that for a large class of black holes, such "horizon constraints" allow the use of conformal field theory techniques to compute the density of states, reproducing the Bekenstein-Hawking entropy in a nearly model-independent manner. One standard string theory approach to black hole entropy arises as a special case, lending support to the claim that the mechanism may be "universal." I argue that the relevant degrees of freedom are Goldstone-boson-like excitations arising from the weak breaking of symmetry by the constraints.     

The stability of fundamental constants

The tests of the constancy of fundamental constants are tests of the local position invariance and thus of the equivalence principle, at the heart of general relativity. After summarising the links between fundamental constants, gravity, cosmology and metrology, a brief overview of the observational and experimental constraints on their variation is proposed.     

Black hole memory

We discuss the formation of black holes during the very early stages of a universe in which the gravitational constant evolves with time. We argue that black holes will retain memory of the value of the gravitational constant,G, at the time of their formation. Their horizon size and their thermal characteristics are determined by the value ofG when they form, not by the value we measure in the external universe today. The observational effects of primordial black hole explosions are therefore radically altered.This essay received the fourth award from the Gravity Research Foundation, 1993—Ed.     

Black hole entropy quantization

Ever since the pioneering works of Bekenstein and Hawking, black hole entropy has been known to have a quantum origin. Furthermore, it has long been argued by Bekenstein that entropy should be quantized in discrete (equidistant) steps given its identification with horizon area in (semi-)classical general relativity and the properties of area as an adiabatic invariant. This lead to the suggestion that the black hole area should also be quantized in equidistant steps to account for the discrete black hole entropy. Here we shall show that loop quantum gravity, in which area is not quantized in equidistant steps, can nevertheless be consistent with Bekenstein's equidistant entropy proposal in a subtle way. For that we perform a detailed analysis of the number of microstates compatible with a given area and show consistency with the Bekenstein framework when an oscillatory behavior in the entropy-area relation is properly interpreted.     

Physical constants as cosmological constraints

A solution to the primary “missing mass” problem is found in the context of accounting for the coincidence of large dimensionless numbers first noticed by Weyl, Eddington, and Dirac. This solution entails (1) a log₂ relation between the electromagnetic and gravitational coupling constants; (2) setting the maximum radius of curvature at the gravitational radius, 2GM/c ²; (3) a changing gravitational parameterG, which varies as an inverse function of the universal radius of curvature. These features motivate the development of a neo-Friedmann formalism, which employs a function,ε(χ). governing the change from Euclidian to non-Euclidian volumes. Observational consequences include (1) a universal density of 7.6×10^?31g cm^?3, (2) a Hubble parameter of 15 km s^?1 Mpc^?1, (3) an age of the universe of 32×10⁹ yr, (4) a gravitational parameter diminishing at a current rate of 2.2×10^?12 yr^?1, and (5) a deceleration parameter of 1.93. Moreover, it is shown that for a Friedmann-type (λ=0) cosmology (whether open or closed) any deceleration parameter will be represented by a straight line in the (log-log) red shift: luminosity-distance space of the Hubble diagram. The major claim of this paper is that we have devised a model in which the large-scale structure of the universe is completely determined by the values of the fundamental physical constants:c, h, e, andm _e setting the scale, andG selecting the epoch.     

黑洞信息佯谬

黑洞信息佯谬作为理论物理领域最著名的问题之一,长期以来一直被认为是研究量子引力的重要途径。黑洞信息佯谬的一个核心问题是给出在黑洞蒸发过程中的佩奇曲线行为。近一年,对该问题的研究迎来了突破性进展。研究人员第一次在半经典引力框架下实现了对佩奇曲线的计算,表明黑洞在蒸发过程中信息可以被释放出来,不存在信息丢失问题。文章将按照历史发展的顺序,对黑洞信息佯谬这一重要问题以及最新进展进行介绍,包括霍金辐射、佩奇曲线、全息原理、广义熵、量子极端面和量子极端孤岛等重要内容。     

Improved spectroscopic constants for the NO fundamental

A power series in the rotational index m has been fitted to the two fundamental $\text{(}{}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{?}{}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{and}{}^2\text{Π}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{?}{}^2\text{Π}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{)}$ bands of nitric oxide and improved effective values of the spectroscopic constants B, D and H were obtained.     

Astrophysics,atomic clocks and fundamental constants

The paper gives a brief introduction to the special topicvolume.     

A probability law for the fundamental constants

If all the fundamental constants x of physics were expressed in one set of units (e.g., mks) and then used as pure numbers in one overall histogram, what shape would that histogram have? Based on some invariances that the law should reasonably obey, we show that it should have either an x^?1 or an x^?2 dependence. Empirical evidence consisting of the presently known constants is consistent with an x^?1 law. This is independent of the system of units chosen for the constants. The existence of the law suggests that the fundamental constants may have been independently and randomly chosen, at creation, from it, and hence that at the next “big bang” randomly a different set will be produced. Also, because of the law, the number 1.0 has an interesting cosmological property: it is the theoretical median of all the fundamental constants. Finally, as a practical matter, the law predicts that current methods of evaluating the fundamental constants are biased toward overly large numbers. A correction term is given for each of three kinds of noise.     

Black hole binaries and microquasars

This is a general review Oil the observations and physics of black hole X-ray binaries and microquasars, with the emphasize on recent developments in the high energy regime. The focus is put on understanding the accretion flows and measuring the parameters of black holes in them. It includes mainly two parts： i） Brief review of several recent review article on this subject; ii） Further development on several topics, including black hole spin measurements, hot accretion flows, corona formation, state transitions and thermal stability of standard think disk. This is thus not a regular bottom-up approach, which I feel not necessary at this stage. Major effort is made in making and incorporating from many sources useful plots and illustrations, in order to make this article more comprehensible to non-expert readers. In the end I attempt to make a unification scheme on the accretion-outflow （wind/jet） connections of all types of aecreting BHs of all accretion rates and all BH mass scales, and finally provide a brief outlook.     

Black hole quantum tunnelling and black hole entropy correction

The Parikh–Wilczek tunnelling framework, which treats Hawking radiation as a tunnelling process, is investigated once more in this work. The first order correction, the log-corrected entropy-area relation, emerges naturally in the tunnelling picture if we consider the emission of a spherical shell. The second order correction to the emission rate for the Schwarzschild black hole is also calculated. At this level, the entropy of the black hole will contain three parts: the usual Bekenstein–Hawking entropy, a logarithmic term and an inverse area term. We find that the coefficient of the logarithmic term is −1. Thus, apart from a coefficient, our correction to the black hole entropy is consistent with that calculated in loop quantum gravity.     

Black hole vacua and rotation

Recent developments suggest that the near-region of rotating black holes behaves like a CFT. To understand this better, I propose to study quantum fields in this region. An instructive approach for this might be to put a large black hole in AdS and to think of the entire geometry as a toy model for the “near-region”. Quantum field theory on rotating black holes in AdS can be well-defined (unlike in flat space), if fields are quantized in the co-rotating-with-the-horizon frame. First, some generalities of constructing Hartle–Hawking Green functions in this approach are discussed. Then as a specific example where the details are easy to handle, I turn to 2+1$2+1$ dimensions (BTZ), write down the Green functions explicitly starting with the co-rotating frame, and observe some structural similarities they have with the Kerr-CFT scattering amplitudes. Finally, in BTZ, there is also an alternate construction for the Green functions: we can start from the covering AdS₃${\mathit{AdS}}_3$ space and use the method of images. Using a 19th century integral formula, I show the equality between the boundary correlators arising via the two constructions.     

Adjusted recommended values of the fundamental physical constants

A brief overview of the CODATA-2006 adjustment (P.J. Mohr, B.N. Taylor, and D.B. Newell, CODATA Recommended values of the fundamental physical constants: 2006, Rev. Mod. Phys. 80, (2008) 633) is presented. The attention is focussed on the most important data that appeared since the previous adjustment in 2002, and on changes in the recommended values of 2006 in comparison with the results of 2002. We consider a structure of the input data and their correlations and analyze the results and the data group by group. We also discuss consequences of the adjustment.     

Hydrogenic systems,frequency standards and fundamental constants

Hydrogenic (two-body) systems are the only atomic systems for which uncertainties in calculations of the energy levels approach the current state of the art in frequency measurement. This article discusses progress in the theory and measurement of transition frequencies in hydrogenic systems. These studies have relevance to the determination of fundamental constants and the testing of physical theories, especially quantum electrodynamics. A set of high accuracy calculable frequency standards could also be realized by using hydrogenic systems.