7,366 research outputs found
Fermion Masses from SO(10) Hermitian Matrices
Masses of fermions in the SO(10) 16-plet are constructed using only the 10,
120 and 126 scalar multiplets. The mass matrices are restricted to be hermitian
and the theory is constructed to have certain assumed quark masses, charged
lepton masses and CKM matrix in accord with data. The remaining free parameters
are found by fitting to light neutrino masses and MSN matrices result as
predictions.Comment: 23 pages. Small textual additions for clarification; formalism and
results unchanged. Version to appear in Phys. Rev.
Determination of the zeta potential for highly charged colloidal suspensions
We compute the electrostatic potential at the surface, or zeta potential
, of a charged particle embedded in a colloidal suspension using a
hybrid mesoscopic model. We show that for weakly perturbing electric fields,
the value of obtained at steady state during electrophoresis is
statistically indistinguishable from in thermodynamic equilibrium. We
quantify the effect of counterions concentration on . We also evaluate
the relevance of the lattice resolution for the calculation of and
discuss how to identify the effective electrostatic radius.Comment: 8 pages, 3 figures with 2 panel
Ab initio Molecular Dynamics in Adaptive Coordinates
We present a new formulation of ab initio molecular dynamics which exploits
the efficiency of plane waves in adaptive curvilinear coordinates, and thus
provides an accurate treatment of first-row elements. The method is used to
perform a molecular dynamics simulation of the CO_2 molecule, and allows to
reproduce detailed features of its vibrational spectrum such as the splitting
of the Raman sigma+_g mode caused by Fermi resonance. This new approach opens
the way to highly accurate ab initio simulations of organic compounds.Comment: 11 pages, 3 PostScript figure
Probing anisotropies of gravitational-wave backgroundswith a space-based interferometer II: Perturbative reconstruction of a low-frequency skymap
We present a perturbative reconstruction method to make a skymap of
gravitational-wave backgrounds (GWBs) observed via space-based interferometer.
In the presence of anisotropies in GWBs, the cross-correlated signals of
observed GWBs are inherently time-dependent due to the non-stationarity of the
gravitational-wave detector. Since the cross-correlated signal is obtained
through an all-sky integral of primary signals convolving with the antenna
pattern function of gravitational-wave detectors, the non-stationarity of
cross-correlated signals, together with full knowledge of antenna pattern
functions, can be used to reconstruct an intensity map of the GWBs. Here, we
give two simple methods to reconstruct a skymap of GWBs based on the
perturbative expansion in low-frequency regime. The first one is based on
harmonic-Fourier representation of data streams and the second is based on
"direct" time-series data. The latter method enables us to create a skymap in a
direct manner. The reconstruction technique is demonstrated in the case of the
Galactic gravitational wave background observed via planned space
interferometer, LISA. Although the angular resolution of low-frequency skymap
is rather restricted, the methodology presented here would be helpful in
discriminating the GWBs of galactic origins by those of the extragalactic
and/or cosmological origins.Comment: 23 pages, 12 figures, Phys.Rev.D (2005) in pres
Transmission and Reflection of Bose-Einstein Condensates Incident on a Gaussian Potential Barrier
We investigate how Bose-Einstein condensates, whose initial state is either
irrotational or contains a single vortex, scatter off a one-dimensional
Gaussian potential barrier. We find that for low atom densities the vortex
structure within the condensate is maintained during scattering, whereas at
medium and high densities, multiple additional vortices can be created by the
scattering process, resulting in complex dynamics and disruption of the atom
cloud. This disruption originates from two different mechanisms associated
respectively with the initial rotation of the atom cloud and the interference
between the incident and reflected matter waves. We investigate how the
reflection probability depends on the vorticity of the initial state and on the
incident velocity of the Bose-Einstein condensate. To interpret our results, we
derive a general analytical expression for the reflection coefficient of a
rotating Bose-Einstein condensate that scatters off a spatially-varying
one-dimensional potential.Comment: 9 pages, 9 figure
A Solution of the Maxwell-Dirac Equations in 3+1 Dimensions
We investigate a class of localized, stationary, particular numerical
solutions to the Maxwell-Dirac system of classical nonlinear field equations.
The solutions are discrete energy eigenstates bound predominantly by the
self-produced electric field.Comment: 12 pages, revtex, 2 figure
Bloch oscillations of Bose-Einstein condensates: Quantum counterpart of dynamical instability
We study the Bloch dynamics of a quasi one-dimensional Bose-Einstein
condensate of cold atoms in a tilted optical lattice modeled by a Hamiltonian
of Bose-Hubbard type: The corresponding mean-field system described by a
discrete nonlinear Schr\"odinger equation can show a dynamical (or modulation)
instability due to chaotic dynamics and equipartition over the quasimomentum
modes. It is shown, that these phenomena are related to a depletion of the
Floquet-Bogoliubov states and a decoherence of the condensate in the
many-particle description. Three different types of dynamics are distinguished:
(i) decaying oscillations in the region of dynamical instability, and (ii)
persisting Bloch oscillations or (iii) periodic decay and revivals in the
region of stability.Comment: 12 pages, 14 figure
An Extension of the Fluctuation Theorem
Heat fluctuations are studied in a dissipative system with both mechanical
and stochastic components for a simple model: a Brownian particle dragged
through water by a moving potential. An extended stationary state fluctuation
theorem is derived. For infinite time, this reduces to the conventional
fluctuation theorem only for small fluctuations; for large fluctuations, it
gives a much larger ratio of the probabilities of the particle to absorb rather
than supply heat. This persists for finite times and should be observable in
experiments similar to a recent one of Wang et al.Comment: 12 pages, 1 eps figure in color (though intelligible in black and
white
Locating the source of projectile fluid droplets
The ill-posed projectile problem of finding the source height from spattered
droplets of viscous fluid is a longstanding obstacle to accident reconstruction
and crime scene analysis. It is widely known how to infer the impact angle of
droplets on a surface from the elongation of their impact profiles. However,
the lack of velocity information makes finding the height of the origin from
the impact position and angle of individual drops not possible. From aggregate
statistics of the spatter and basic equations of projectile motion, we
introduce a reciprocal correlation plot that is effective when the polar launch
angle is concentrated in a narrow range. The vertical coordinate depends on the
orientation of the spattered surface, and equals the tangent of the impact
angle for a level surface. When the horizontal plot coordinate is twice the
reciprocal of the impact distance, we can infer the source height as the slope
of the data points in the reciprocal correlation plot. If the distribution of
launch angles is not narrow, failure of the method is evident in the lack of
linear correlation. We perform a number of experimental trials, as well as
numerical calculations and show that the height estimate is insensitive to
aerodynamic drag. Besides its possible relevance for crime investigation,
reciprocal-plot analysis of spatter may find application to volcanism and other
topics and is most immediately applicable for undergraduate science and
engineering students in the context of crime-scene analysis.Comment: To appear in the American Journal of Physics (ms 23338). Improved
readability and organization in this versio
Numerical computation of real or complex elliptic integrals
Algorithms for numerical computation of symmetric elliptic integrals of all
three kinds are improved in several ways and extended to complex values of the
variables (with some restrictions in the case of the integral of the third
kind). Numerical check values, consistency checks, and relations to Legendre's
integrals and Bulirsch's integrals are included
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