15,760 research outputs found
Monte Carlo Quasi-Heatbath by approximate inversion
When sampling the distribution P(phi) ~ exp(-|A phi|^2), a global heatbath
normally proceeds by solving the linear system A phi = eta, where eta is a
normal Gaussian vector, exactly. This paper shows how to preserve the
distribution P(phi) while solving the linear system with arbitrarily low
accuracy. Generalizations are presented.Comment: 10 pages, 1 figure; typos corrected, reference added; version to
appear in Phys. Rev.
Correction-to-scaling exponent for two-dimensional percolation
We show that the correction-to-scaling exponents in two-dimensional
percolation are bounded by Omega <= 72/91, omega = D Omega <= 3/2, and Delta_1
= nu omega <= 2, based upon Cardy's result for the critical crossing
probability on an annulus. The upper bounds are consistent with many previous
measurements of site percolation on square and triangular lattices, and new
measurements for bond percolation presented here, suggesting this result is
exact. A scaling form evidently applicable to site percolation is also found
Why we kill: understanding violence across cultures and disciplines
Infanticide, serial killings, war, terrorism, abortion, honour killings, euthanasia, suicide bombings and genocide; all involve taking of life. Put most simply, all involve killing one or more other people. Yet cultural context influences heavily how one perceives all of these, and indeed, some readers of this paragraph may already have thought: 'But surely that doesn't belong with those others, that's not really killing.'
For such an evolved species, human beings can be violent far beyond the point of inhumanity. Why We Kill: Understanding violence across cultures and disciplines examines this violence in many of its manifestations, exploring how culture plays a role in people's understanding of violent action.
From the first chapter, which tries to understand multiple forms of domestic homicide including infanticide, filicide, spousal homicide and honour killings, to the final chapter's bone-chilling account of the massacre at Murambi in Rwanda, this fascinating book makes compelling reading
PHENIX Measurement of High- Hadron-hadron and Photon-hadron Azimuthal Correlations
High- hadron-hadron correlations have been measured with the PHENIX
experiment in \Cu and \pp collisions at GeV. A
comparison of the jet widths and yields between the two colliding systems
allows us to study the medium effect on jets. We also present a first
measurement of direct photon-hadron correlations in \Au and \pp collisions.
We find that the near-side yields are consistent with zero in both systems. By
comparing the jet yields on the away side, we observe a suggestion of the
expected suppression of hadrons associated with photons in \Au collisions.Comment: 5 pages, proceeding for parallel talk on Quark Matter 200
Weisskopf-Wigner Decay Theory for the Energy-Driven Stochastic Schr\"odinger Equation
We generalize the Weisskopf-Wigner theory for the line shape and transition
rates of decaying states to the case of the energy-driven stochastic
Schr\"odinger equation that has been used as a phenomenology for state vector
reduction. Within the standard approximations used in the Weisskopf-Wigner
analysis, and assuming that the perturbing potential inducing the decay has
vanishing matrix elements within the degenerate manifold containing the
decaying state, the stochastic Schr\"odinger equation linearizes. Solving the
linearized equations, we find no change from the standard analysis in the line
shape or the transition rate per unit time. The only effect of the stochastic
terms is to alter the early time transient behavior of the decay, in a way that
eliminates the quantum Zeno effect. We apply our results to estimate
experimental bounds on the parameter governing the stochastic effects.Comment: 29 pages in RevTeX, Added Note, references adde
Probability distribution of the maximum of a smooth temporal signal
We present an approximate calculation for the distribution of the maximum of
a smooth stationary temporal signal X(t). As an application, we compute the
persistence exponent associated to the probability that the process remains
below a non-zero level M. When X(t) is a Gaussian process, our results are
expressed explicitly in terms of the two-time correlation function,
f(t)=.Comment: Final version (1 major typo corrected; better introduction). Accepted
in Phys. Rev. Let
The Kepler problem and non commutativity
We investigate the Kepler problem using a symplectic structure consistent
with the commutation rules of the noncommutative quantum mechanics. We show
that a noncommutative parameter of the order of gives
observable corrections to the movement of the solar system. In this way,
modifications in the physics of smaller scales implies modifications at large
scales, something similar to the UV/IR mixing.Comment: 10 page
Quantum Black Holes as the Link Between Microphysics and Macrophysics
There appears to be a duality between elementary particles, which span the
mass range below the Planck scale, and black holes, which span the mass range
range above it. In particular, the Black Hole Uncertainty Principle
Correspondence posits a smooth transition between the Compton and Schwarzschild
scales as a function of mass. This suggests that all black holes are in some
sense quantum, that elementary particles can be interpreted as sub-Planckian
black holes, and that there is a subtle connection between quantum and
classical physics.Comment: 9 pages, 7 figures, 2015 Karl Schwarzschild Meeting on Gravitational
Physics, eds. P. Nicolini, J. Mureika, M. Kaminski and M. Bleiche
Breaking quantum linearity: constraints from human perception and cosmological implications
Resolving the tension between quantum superpositions and the uniqueness of
the classical world is a major open problem. One possibility, which is
extensively explored both theoretically and experimentally, is that quantum
linearity breaks above a given scale. Theoretically, this possibility is
predicted by collapse models. They provide quantitative information on where
violations of the superposition principle become manifest. Here we show that
the lower bound on the collapse parameter lambda, coming from the analysis of
the human visual process, is ~ 7 +/- 2 orders of magnitude stronger than the
original bound, in agreement with more recent analysis. This implies that the
collapse becomes effective with systems containing ~ 10^4 - 10^5 nucleons, and
thus falls within the range of testability with present-day technology. We also
compare the spectrum of the collapsing field with those of known cosmological
fields, showing that a typical cosmological random field can yield an efficient
wave function collapse.Comment: 13 pages, LaTeX, 3 figure
Gravitomagnetism in Quantum Mechanics
We give a systematic treatment of the quantum mechanics of a spin zero
particle in a combined electromagnetic field and a weak gravitational field,
which is produced by a slow moving matter source. The analysis is based on the
Klein-Gordon equation expressed in generally covariant form and coupled
minimally to the electromagnetic field. The Klein-Gordon equation is recast
into Schroedinger equation form (SEF), which we then analyze in the
non-relativistic limit. We include a discussion of some rather general
observable physical effects implied by the SEF, concentrating on
gravitomagnetism. Of particular interest is the interaction of the orbital
angular momentum of the particle with the gravitomagnetic field.Comment: 9 page
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