23,712 research outputs found
Universality class of the depinning transition in the two-dimensional Ising model with quenched disorder
With Monte Carlo methods, we investigate the universality class of the
depinning transition in the two-dimensional Ising model with quenched random
fields. Based on the short-time dynamic approach, we accurately determine the
depinning transition field and both static and dynamic critical exponents. The
critical exponents vary significantly with the form and strength of the random
fields, but exhibit independence on the updating schemes of the Monte Carlo
algorithm. From the roughness exponents and , one
may judge that the depinning transition of the random-field Ising model belongs
to the new dynamic universality class with
and . The crossover from the second-order phase transition
to the first-order one is observed for the uniform distribution of the random
fields, but it is not present for the Gaussian distribution.Comment: 16 pages, 16 figures, 3 table
Are the New Physics Contributions from the Left-Right Symmetric Model Important for the Indirect CP Violation in the Neutral B Mesons?
Several works analyzing the new physics contributions from the Left-Right
Symmetric Model to the CP violation phenomena in the neutral B mesons can be
found in the literature. These works exhibit interesting and experimentally
sensible deviations from the Standard Model predictions but at the expense of
considering a low right scale \upsilon_R around 1 TeV. However, when we stick
to the more conservative estimates for \upsilon_R which say that it must be at
least 10^7 GeV, no experimentally sensible deviations from the Standard Model
appear for indirect CP violation. This estimate for \upsilon_R arises when the
generation of neutrino masses is considered. In spite of the fact that this
scenario is much less interesting and says nothing new about both the CP
violation phenomenon and the structure of the Left-Right Symmetric Model, this
possibility must be taken into account for the sake of completeness and when
considering the see-saw mechanism that provides masses to the neutrino sector.Comment: LaTex file. 19 pages, 4 figures. Change in the way the paper address
the problem. As a result, change in title, abstract, and some sections.
Conclusions unchanged. Version to appear in Foundations of Physics Letter
The two Ultraluminous X-ray sources in the galaxy NGC 925
NGC 925 ULX-1 and ULX-2 are two ultraluminous X-ray sources in the galaxy NGC
925, at a distance of 8.5 Mpc. For the first time, we analyzed high quality,
simultaneous XMM-Newton and NuSTAR data of both sources. Although at a first
glance ULX-1 resembles an intermediate mass black hole candidate (IMBH) because
of its high X-ray luminosity ( erg s) and its
spectral/temporal features, a closer inspection shows that its properties are
more similar to those of a typical super-Eddington accreting stellar black hole
and we classify it as a `broadened disc' ultraluminous X-ray source. Based on
the physical interpretation of this spectral state, we suggest that ULX-1 is
seen at small inclination angles, possibly through the evacuated cone of a
powerful wind originating in the accretion disc. The spectral classification of
ULX-2 is less certain, but we disfavour an IMBH accreting at sub-Eddington
rates as none of its spectral/temporal properties can be associated to either
the soft or hard state of Galactic accreting black hole binaries.Comment: Accepted on MNRAS with very minor comments, 7 pages, 5 figures, 1
tabl
Necessary and sufficient detection efficiency for the Mermin inequalities
We prove that the threshold detection efficiency for a loophole-free Bell
experiment using an -qubit Greenberger-Horne-Zeilinger state and the
correlations appearing in the -partite Mermin inequality is . If
the detection efficiency is equal to or lower than this value, there are local
hidden variable models that can simulate all the quantum predictions. If the
detection efficiency is above this value, there is no local hidden variable
model that can simulate all the quantum predictions.Comment: REVTeX4, 5 pages, 1 figur
Examples of q-regularization
An Introduction to Hopf algebras as a tool for the regularization of relavent
quantities in quantum field theory is given. We deform algebraic spaces by
introducing q as a regulator of a non-commutative and non-cocommutative Hopf
algebra. Relevant quantities are finite provided q\neq 1 and diverge in the
limit q\rightarrow 1. We discuss q-regularization on different q-deformed
spaces for \lambda\phi^4 theory as example to illustrate the idea.Comment: 17 pages, LaTex, to be published in IJTP 1995.1
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