119274399
Kerr–Newman black hole thermodynamical state space: blockwise coordinates
A coordinate system that blockwise-simplifies the Kerr–Newman black hole’s thermodynamical state space Ruppeiner metric geometry is constructed, with discussion of the limiting cases corresponding to simpler black holes. It is deduced that one of the three conformal Killing vectors of the Reissner–Nordström and Kerr cases (whose thermodynamical state space metrics are 2 by 2 and conformally flat) survives generalization to the Kerr–Newman case’s 3 by 3 thermodynamical state space metric.
118427409
The Problem of Time and Quantum Cosmology in the Relational Particle Mechanics Arena
This article contains a local solution to the notorious Problem of Time in Quantum Gravity at the conceptual level and which is actually realizable for the relational triangle. The Problem of Time is that `time' in GR and `time' in ordinary quantum theory are mutually incompatible notions, which is problematic in trying to put these two theories together to form a theory of Quantum Gravity. Four frontiers to this resolution in full GR are identified, alongside three further directions not yet conquered even for the relational triangle. 
This article is also the definitive review on relational particle models originally due to Barbour (2003: dynamics of pure shape) and Barbour and Bertotti (1982: dynamics of shape and scale). These are exhibited as useful toy models of background independence, which I argue to be the `other half' of GR to relativistic gravitation, as well as the originator of the Problem of Time itself. Barbour's work and my localized extension of it are shown to be the classical precursor of the background independence that then manifests itself at the quantum level as the full-blown Problem of Time. In fact 7/8ths of the Isham--Kuchar Problem of Time facets are already present in classical GR; even classical mechanics in relational particle mechanics formulation exhibits 5/8ths of these! In addition to Isham, Kuchar and Barbour, the other principal authors whose works are drawn upon in building this Problem of Time approach are Kendall (relational models only: pure-shape configuration spaces), Dirac, Teitelboim and Halliwell (Problem of Time resolving components). The recommended scheme is a combination of the Machian semiclassical approach, histories theory and records theory.
119476891
The physical gravitational degrees of freedom
When constructing general relativity (GR), Einstein required 4D general covariance. In contrast, we derive GR (in the compact, without boundary case) as a theory of evolving three-dimensional conformal Riemannian geometries obtained by imposing two general principles: (1) time is derived from change; (2) motion and size are relative. We write down an explicit action based on them. We obtain not only GR in the CMC gauge, in its Hamiltonian 3 + 1 reformulation, but also all the equations used in York's conformal technique for solving the initial-value problem. This shows that the independent gravitational degrees of freedom obtained by York do not arise from a gauge fixing but from hitherto unrecognized fundamental symmetry principles. They can therefore be identified as the long-sought Hamiltonian physical gravitational degrees of freedom.
119222489
Scaled Triangleland Model of Quantum Cosmology
In scaled relational particle mechanics, only relative times, relative angles and relative separations are meaningful. It arose in the study of the absolute versus relative motion debate. It has then turned out to be a useful toy model of classical and quantum general relativity, such as for investigating conceptual strategies for the problem of time. This paper studies the 3-particle 2-d scaled relational particle model, for which the configurations are scaled triangles. The configuration space for these is R^3 with a conformally flat metric thereupon (it is the cone over the corresponding shape space S^2. I use multiple harmonic oscillator type potentials and other potentials suggested by analogy with cosmology, and solve for some of these by using a partial analogy with the treatment of the atom in spherical and parabolic coordinates. Spherical coordinates are here the total moment of inertia $I$ for radius and two pure-shape coordinates. These are \Theta, a function of the ratio of the two relative separations of subsystems, and \Phi, the relative angle between the two subsystems. Parabolic coordinates are \Phi again and twice the partial moments of inertia of each subsystem. I interpret these solutions using 1) a `Bohr moment of inertia' for the model universe (playing the role of the scalefactor). 2) Expectations and spreads of sizes and shapes. 3) Superimposing the probability density function on the labelled tessellation of the configuration space that encodes meaningful subregions such as collinear configurations, equilateral triangles and isosceles triangles. Applications include hidden time, emergent semiclassical time, timeless and histories theory problem of time strategies, and comparing reduced and Dirac methods of quantization.
56380776
Problem of time in quantum gravity
The Problem of Time occurs because the ‘time’ of GR and of ordinary Quantum Theory are mutually incompatible notions. This is problematic in trying to replace these two branches of physics with a single framework in situations in which the conditions of both apply, e.g. in black holes or in the very early universe. Emphasis in this Review is on the Problem of Time being multi-faceted and on the nature of each of the eight principal facets. Namely, the Frozen Formalism Problem, Configurational Relationalism Problem (formerly Sandwich Problem), Foliation Dependence Problem, Constraint Closure Problem (formerly Functional Evolution Problem), Multiple Choice Problem, Global Problem of Time, Problem of Beables (alias Problem of Observables) and Spacetime Reconstruction/Replacement Problem. Strategizing in this Review is not just centred about the Frozen Formalism Problem facet, but rather about each of the eight facets. Particular emphasis is placed upon A) relationalism as an underpinning of the facets and as a selector of particular strategies (especially a modification of Barbour relationalism, though also with some consideration of Rovelli relationalism). B) Classifying approaches by the full ordering in which they embrace constrain, quantize, find time/history and find observables, rather than only by partial orderings such as “Dirac-quantize”. C) Foliation (in)dependence and Spacetime Reconstruction for a wide range of physical theories, strategizing centred about the Problem of Beables, the Patching Approach to the Global Problem of Time, and the role of the question-types considered in physics. D) The Halliwell- and Gambini–Porto–Pullin-type combined Strategies in the context of semiclassical quantum cosmology.
95866
Quantum cosmological metroland model
Relational particle mechanics is useful for modelling whole-universe issues such as quantum cosmology or the problem of time in quantum gravity, including some aspects outside the reach of comparably complex mini-superspace models. In this paper, we consider the mechanics of pure shape and not scale of four particles on a line, so that the only physically significant quantities are ratios of relative separations between the constituents' physical objects. Many of our ideas and workings extend to the N-particle case. As such models' configurations resemble depictions of metro lines in public transport maps, we term them 'N-stop metrolands'. This 4-stop model's configuration space is a 2-sphere, from which our metroland mechanics interpretation is via the 'cubic' tessellation. This model yields conserved quantities which are mathematically SO(3) objects like angular momenta but are physically relative dilational momenta (i.e. coordinates dotted with momenta). We provide and interpret various exact and approximate classical and quantum solutions for 4-stop metroland; from these results one can construct expectations and spreads of shape operators that admit interpretations as relative sizes and the 'homogeneity of the model universe's contents', and also objects of significance for the problem of time in quantum gravity (e.g. in the naive Schrodinger and records theory timeless approaches).
119492806
The on-line satellite/central computer facility of the Multiparticle Argo Spectrometer System
Abstract An on-line satellite/central computer facility has been developed at Brookhaven National Laboratory as part of the Multiparticle Argo Spectrometer System (MASS). This facility, consisting of a PDP-9 and a CDC-6600, has been successfully used in a study of proton-proton interactions at 28.5 GeV/ c .
121981552
Observation and study of centrally produced pion clusters in 28. 5-GeV/c p-p interactions
A double-arm spectrometer is used to identify a pion cluster produced in central p-p collisions at 28.5 GeV/c. Cluster properties studied are angular momentum, quantum statistics, multiplicity, and effective mass. There is some speculation on the production mechanism. (AIP)
32865960
Recent advances in low level counting techniques.
Problems involving low level counting techniques are encountered in many diverse fields including biological and chemical tracer studies, archaeo­ logical and geological dating (I), investigations of natural and induced radio­ activities, and the study of fundamental particles. Such a host of methods and variations on methods have been reported that an exhaustive catalog would constitute little more than an annotated bibliography. We have, there­ fore, limited our attention to a few selected examples which seem to be of special interest because of their versatility or their extreme sensitivity. We prefer to organize our discussion around specific problems rather than around types of detectors since this permits a comparison of alternative methods and provides practical examples of various techniques in actual operation. Alpha counting is arbitrarily excluded. For a discussion of photographic methods (radioautographs) the reader is referred to Norris & Woodruff (2) and refer­ ences cited therein. We will discuss the methods developed for the measure­ ment of natural radiocarbon and tritium, cosmic ray produced Be7, and the K(O content of the human body. DOUble-beta decay experiments are consid­ ered since they seem to constitute one of the most difficult of the outstanding problems and because of their importance from the viewpoint of theoretical nuclear physics. Finally, an account is given of recent attempts to detect the neutrino, probably the most difficult low level counting problem of all and one which seems finally on the verge of successful solution. Principles.-The fundamental principles of low level counting are simple: maximize the number of detected events of the desired kind (signal) and minimize all others (background). The number of detected events is, of course, the product of sample size, over-all counting efficiency, and counting time. However, the striking importance of the net sample counting rate is not always fully appreciated. It can be shown (3) from elementary counting statistics, that if the sample rate is small compared with background (which is usually the case in a truly low level problem) and if counting statistics is the limiting source of error (also usually true), then the proper parameter for the comparison of counting methods is S2/B, the ratio of the square of the net sample rate to the background rate. (Any sample strength can be used in making the comparison so long as the same strength is used in testing all methods.) The method giving the maximum value of S2/B will yield the
124078930
Muon Capture in Hydrogen
Abstract : An experiment to measure the muon capture rate in liquid hydrogen was carried out using scintillation counter techniques. The experiment tests muon-electron universality in interaction with a proton at a momentum transfer of 100 MeV/c. The use of ultra-pure liquid hydrogen, a purified muon beam, neutron-gamma ray discriminating detectors and oscilloscope photography made possible the detection of the 5.2 MeV neutron from the relatively improbable capture reaction (mu + p yields n + nu). The muon molecular formation rate was measured in an independent experiment, but the present result is relatively insensitive to it. The stability of the muon molecular ortho state against transitions to the para ground state for times comparable to the free muon life-time is confirmed. The experimental result of the capture rate measurement, 464 + or - 42 per second is compared with 562 + or - 60 per second, the rate expected on the basis of the conserved vector current theory, muon-electron universality and the accepted value of the "induced pseudo scalar" coupling constant.
139640917
Effects of Channel Failure Rates on the Jet Reconstruction Efficiencies an Resolutions in an Fe HF Calorimeter