910 research outputs found
Soft Black Hole Absorption Rates as Conservation Laws
The absorption rate of low-energy, or soft, electromagnetic radiation by
spherically symmetric black holes in arbitrary dimensions is shown to be fixed
by conservation of energy and large gauge transformations. We interpret this
result as the explicit realization of the Hawking-Perry-Strominger Ward
identity for large gauge transformations in the background of a non-evaporating
black hole. Along the way we rederive and extend previous analytic results
regarding the absorption rate for the minimal scalar and the photon.Comment: 20 Pages, 1 figur
C(sp3)−C(sp3) Cross‐Coupling of Alkyl Bromides and Ethers Mediated by Metal and Visible Light Photoredox Catalysis
We report a C(sp(3))-C(sp(3)) cross-coupling of alkyl bromides and alkyl chlorides with ethers by dual photoredox-nickel catalysis. The catalytic system comprises of the organic photocatalyst 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4-CzIPN) and bench stable nickel (II) acetylacetonate in the presence of visible-light, providing the coupling products in up to 92% yield. Preliminary mechanistic studies suggest two catalytic cycles, as well as the photogeneration of bromine or chlorine radicals from halide atoms that are present in the structures of the coupling partners. The halide radical mediates the hydrogen atom transfer event, avoiding the need of an additional HAT catalyst
Orthopädische Biomechanik
Das Buch beschreibt Gedankengänge und Vorgehensweisen der orthopädischen Biomechanik, den Kenntnisstand zu Belastung und Beanspruchung des Haltungs- und Bewegungsapparates sowie die Reaktion der Gewebe auf mechanische Einflüsse exakt, aber mit einem Minimum an mathematischer und physikalischer Argumentation. Es gliedert sich in die Abschnitte
I Grundlagen aus der Mechanik
II Grundlagen aus der Mathematik
III Mechanische Aspekte des Haltungs- und Bewegungsapparates
IV Übungsaufgaben mit ausgearbeiteten Lösungen
Zahlreiche Abbildungen unterstützen die anschauliche Darstellung.
Ein Buch für Orthopäden, Ingenieure, Naturwissenschaftler, Physiotherapeuten und Orthopädietechniker in den Bereichen Forschung und Entwicklung von Orthopädie und Rehabilitation. <br/
Lowering of the Kinetic Energy in Interacting Quantum Systems
Interactions never lower the ground state kinetic energy of a quantum system.
However, at nonzero temperature, where the system occupies a thermal
distribution of states, interactions can reduce the kinetic energy below the
noninteracting value. This can be demonstrated from a first order weak coupling
expansion. Simulations (both variational and restricted path integral Monte
Carlo) of the electron gas model and dense hydrogen confirm this and show that
in contrast to the ground state case, at nonzero temperature the population of
low momentum states can be increased relative to the free Fermi distribution.
This effect is not seen in simulations of liquid He-3.Comment: 4 pages, 5 figures, submitted to Phys. Rev. Lett., June, 200
Static black hole solutions with axial symmetry
We construct a new class of asymptotically flat black hole solutions in
Einstein-Yang-Mills and Einstein-Yang-Mills-dilaton theory. These black hole
solutions are static, and they have a regular event horizon. However, they
possess only axial symmetry. Like their regular counterparts, the black hole
solutions are characterized by two integers, the winding number and the
node number of the gauge field functions.Comment: 14 pages, including 4 postscript figures, LaTe
Variational Density Matrix Method for Warm Condensed Matter and Application to Dense Hydrogen
A new variational principle for optimizing thermal density matrices is
introduced. As a first application, the variational many body density matrix is
written as a determinant of one body density matrices, which are approximated
by Gaussians with the mean, width and amplitude as variational parameters. The
method is illustrated for the particle in an external field problem, the
hydrogen molecule and dense hydrogen where the molecular, the dissociated and
the plasma regime are described. Structural and thermodynamic properties
(energy, equation of state and shock Hugoniot) are presented.Comment: 26 pages, 13 figures. submitted to Phys. Rev. E, October 199
Static Axially Symmetric Solutions of Einstein-Yang-Mills-Dilaton Theory
We construct static axially symmetric solutions of SU(2)
Einstein-Yang-Mills-dilaton theory. Like their spherically symmetric
counterparts, these solutions are nonsingular and asymptotically flat. The
solutions are characterized by the winding number n and the node number k of
the gauge field functions. For fixed n with increasing k the solutions tend to
``extremal'' Einstein-Maxwell-dilaton black holes with n units of magnetic
charge.Comment: 11 pages, including 2 postscript figure
High-statistics finite size scaling analysis of U(1) lattice gauge theory with Wilson action
We describe the results of a systematic high-statistics Monte-Carlo study of
finite-size effects at the phase transition of compact U(1) lattice gauge
theory with Wilson action on a hypercubic lattice with periodic boundary
conditions. We find unambiguously that the critical exponent nu is lattice-size
dependent for volumes ranging from 4^4 to 12^4. Asymptotic scaling formulas
yield values decreasing from nu(L >= 4) = 0.33 to nu(L >= 9) = 0.29. Our
statistics are sufficient to allow the study of different phenomenological
scenarios for the corrections to asymptotic scaling. We find evidence that
corrections to a first-order transition with nu=0.25 provide the most accurate
description of the data. However the corrections do not follow always the
expected first-order pattern of a series expansion in the inverse lattice
volume V^{-1}. Reaching the asymptotic regime will require lattice sizes
greater than L=12. Our conclusions are supported by the study of many cumulants
which all yield consistent results after proper interpretation.Comment: revtex, 12 pages, 9 figure
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