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Search Results: 1 - 10 of 147881 matches for " Joshua B. Halpern "
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Comment on: Increasing Exclusion: The Pauli Exclusion Principle and Energy Conservation for Bound Fermions are Mutually Exclusive arXiv:physics/0609190v4 [physics.gen-ph] by Jonathan Phillips
Joshua B. Halpern
Physics , 2007,
Abstract: Phillips incorrectly analyzes the ionization of He to conclude that the Pauli exclusion principle and conservation of energy are mutually exclusive. His error arises from neglect of electron repulsion, improper choices of energy zeros and other trivial errors.
Observations and Modeling of the Companions of Short Period Binary Millisecond Pulsars: Evidence for High-Mass Neutron Stars
Joshua Schroeder,Jules Halpern
Physics , 2014, DOI: 10.1088/0004-637X/793/2/78
Abstract: We present observations of fields containing eight recently discovered binary millisecond pulsars using the telescopes at MDM Observatory. Optical counterparts to four of these systems are detected, one of which, PSR J2214+3000, is a novel detection. Additionally, we present the fully phase-resolved B, V, and R light curves of the optical counterparts to two objects, PSR J1810+1744 and PSR J2215+5135 for which we employ model fitting using the ELC model of Orosz & Hauschildt (2000) to measure the unknown system parameters. For PSR J1810+1744 we find that the system parameters cannot be fit even assuming that 100% of the spin-down luminosity of the pulsar is irradiating the secondary, and so radial velocity measurements of this object will be required for the complete solution. However, PSR J2215+5135 exhibits light curves that are extremely well constrained using the ELC model and we find that the mass of the neutron star is constrained by these and the radio observations to be greater than 1.75 solar masses at the 3-sigma level. We also find a discrepancy between the model temperature and the measured colors of this object which we interpret as possible evidence for an additional high-temperature source such as a quiescent disk. Given this and the fact that PSR J2214+5135 contains a relatively high mass companion (greater than 0.1 solar masses), we propose that similar to the binary pulsar systems PSR J1023+0038 and IGR J18245-2452, the pulsar may transition between accretion- and rotation-powered modes.
Electronic and Structural Characteristics of Zinc-Blende Wurtzite Biphasic Homostructure GaN Nanowires
Benjamin W. Jacobs,Virginia M. Ayres,Mihail P. Petkov,Joshua B. Halpern,MaoQe He,Andrew D. Baczewski,Kaylee McElroy,Martin A. Crimp,Jiaming Zhang,Harry C. Shaw
Physics , 2007, DOI: 10.1021/nl062871y
Abstract: We report a new biphasic crystalline wurtzite/zinc-blende homostructure in gallium nitride nanowires. Cathodoluminescence was used to quantitatively measure the wurtzite and zinc-blende band gaps. High resolution transmission electron microscopy was used to identify distinct wurtzite and zinc-blende crystalline phases within single nanowires through the use of selected area electron diffraction, electron dispersive spectroscopy, electron energy loss spectroscopy, and fast Fourier transform techniques. A mechanism for growth is identified.
Recent Progress in Irrational Conformal Field Theory
M. B. Halpern
Physics , 1993,
Abstract: In this talk, I will review the foundations of irrational conformal field theory (ICFT), which includes rational conformal field theory as a small subspace. Highlights of the review include the Virasoro master equation, the Ward identities for the correlators of ICFT and solutions of the Ward identities. In particular, I will discuss the solutions for the correlators of the $g/h$ coset constructions and the correlators of the affine-Sugawara nests on $g\supset h_1 \supset \ldots \supset h_n$. Finally, I will discuss the recent global solution for the correlators of all the ICFT's in the master equation.
The Orbifolds of Permutation-Type as Physical String Systems at Multiples of $\mathbf{c=26}$ V. Cyclic Permutation Orbifolds
M. B. Halpern
Physics , 2007, DOI: 10.1063/1.2824499
Abstract: I consider the $\mathbb{Z}_\lambda,$ $\lambda$ prime free-bosonic permutation orbifolds as interacting physical string systems at $\hat{c} = 26\lambda $. As a first step, I introduce twisted tree diagrams which confirm at the interacting level that the physical spectrum of each twisted sector is equivalent to that of an ordinary $c=26$ closed string. The untwisted sectors are surprisingly more difficult to understand, and there are subtleties in the sewing of the loops, but I am able to propose provisional forms for the full modular-invariant cosmological constants and one-loop diagrams with insertions.
Irrational Conformal Field Theory on the Sphere and the Torus
M. B. Halpern
Physics , 1994,
Abstract: I review the foundations of irrational conformal field theory (ICFT), which includes rational conformal field theory as a small subspace. Highlights of the review include the Virasoro master equation and the generalized Knizhnik-Zamolodchikov equations for the correlators of ICFT on the sphere and the torus.
On the Large N Limit of Conformal Field Theory
M. B. Halpern
Physics , 2002, DOI: 10.1016/S0003-4916(03)00002-2
Abstract: Following recent advances in large N matrix mechanics, I discuss here the free (Cuntz) algebraic formulation of the large N limit of two-dimensional conformal field theories of chiral adjoint fermions and bosons. One of the central results is a new {\it affine free algebra} which describes a large N limit of su(N) affine Lie algebra. Other results include the associated {\it free-algebraic partition functions and characters}, a free-algebraic coset construction, free- algebraic construction of osp(1|2), {\it free-algebraic vertex operator constructions} in the large N Bose systems and a provocative new free-algebraic factorization of the ordinary Koba-Nielsen factor.
The Orbifolds of Permutation-Type as Physical String Systems at Multiples of $c=26$ III. The Spectra of $\hat{c}=52$ Strings
M. B. Halpern
Physics , 2007, DOI: 10.1016/j.nuclphysb.2007.08.001
Abstract: In the second paper of this series, I obtained the twisted BRST systems and extended physical-state conditions of all twisted open and closed $\hat{c} = 52$ strings. In this paper, I supplement the extended physical-state conditions with the explicit form of the extended (twisted) Virasoro generators of all $\hat{c} = 52$ strings, which allows us to discuss the physical spectra of these systems. Surprisingly, all the $\hat{c}=52$ spectra admit an equivalent description in terms of generically-unconventional Virasoro generators at $c=26$. This description strongly supports our prior conjecture that the $\hat{c}=52$ strings are free of negative-norm states, and moreover shows that the spectra of some of the simpler cases are equivalent to those of ordinary untwisted open and closed $c=26$ strings.
The Orbifolds of Permutation-Type as Physical String Systems at Multiples of c=26 IV. Orientation Orbifolds Include Orientifolds
M. B. Halpern
Physics , 2007, DOI: 10.1103/PhysRevD.76.026004
Abstract: In this fourth paper of the series, I clarify the somewhat mysterious relation between the large class of {\it orientation orbifolds} (with twisted open-string CFT's at $\hat c=52$) and {\it orientifolds} (with untwisted open strings at $c=26$), both of which have been associated to division by world-sheet orientation-reversing automorphisms. In particular -- following a spectral clue in the previous paper -- I show that, even as an {\it interacting string system}, a certain half-integer-moded orientation orbifold-string system is in fact equivalent to the archetypal orientifold. The subtitle of this paper, that orientation orbifolds include and generalize standard orientifolds, then follows because there are many other orientation orbifold-string systems -- with higher fractional modeing -- which are not equivalent to untwisted string systems.
The Lorentzian Space-Times of the Orientation-Orbifold String Systems
M. B. Halpern
Physics , 2010,
Abstract: To illustrate our recent discussions of the target space-times in general orbifold-string theories of permutation-type, we return here to a detailed analysis of some simple examples of this type, namely an explicit set of orientation-orbifold string systems. These orientation-orbifold string systems provide twisted, multisector generalizations of ordinary critical open-closed bosonic string systems -- each such system exhibiting a unique graviton. Furthermore, each sector $\sigma$ of these string systems shows the following properties: a) 26 effective degrees of freedom, b) a Lorentzian space-time with space-time dimension $D(\sigma)\leq 26$, c) an $SO(D(\sigma)-1,1)$-invariant ordinary string subsystem with quantized intercept less than or equal one, and d) an extra set of $(26-D(\sigma))$ twisted fields which are $SO(D(\sigma)-1,1)$ scalars. Subexamples of non-tachyonic strings and four-dimensional strings are noted. Additionally, we discuss certain subsets of physical states of these theories, concluding that these investigations are so far consistent with the no-ghost conjecture for all the Lorentzian orbifold-string theories of permutation-type.
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