26,394 research outputs found
Gauge dilution and leptogenesis
In this paper, we examine how gauge interactions can dilute the lepton
asymmetry in lepton induced baryogenesis. Constraints imposed on Majorana
masses keep this dilution at an acceptable level.Comment: 5 page
Rainbow universe
The formalism of rainbow gravity is studied in a cosmological setting. We
consider the very early universe which is radiation dominated. A novel
treatment in our paper is to look for an ``averaged'' cosmological metric
probed by radiation particles themselves. Taking their cosmological evolution
into account, we derive the modified Friedmann-Robertson-Walker(FRW) equations
which is a generalization of the solution presented by Magueijo and Smolin.
Based on this phenomenological cosmological model we argue that the spacetime
curvature has an upper bound such that the cosmological singularity is absent.
These modified equations can be treated as effective equations in the
semi-classical framework of quantum gravity and its analogy with the one
recently proposed in loop quantum cosmology is also discussed.Comment: 5 page
Fate of the Peak Effect in a Type-II Superconductor: Multicriticality in the Bragg-Glass Transition
We have used small-angle-neutron-scattering (SANS) and ac magnetic
susceptibility to investigate the global magnetic field H vs temperature T
phase diagram of a single crystal Nb in which a first-order transition of
Bragg-glass melting (disordering), a peak effect, and surface superconductivity
are all observable. It was found that the disappearance of the peak effect is
directly related to a multicritical behavior in the Bragg-glass transition.
Four characteristic phase boundary lines have been identified on the H-T plane:
a first-order line at high fields, a mean-field-like continuous transition line
at low fields, and two continuous transition line associated with the onset of
surface and bulk superconductivity. All four lines are found to meet at a
multicritical point.Comment: 4 figure
Normal subgroups of diffeomorphism and homeomorphism groups of R^n and other open manifolds
We determine all the normal subgroups of the group of C^r diffeomorphisms of
R^n, r = 1,2,...,infinity, except when r=n+1 or n=4, and also of the group of
homeomorphisms of R^n (r=0). We also study the group A_0 of diffeomorphisms of
an open manifold M that are isotopic to the identity. If M is the interior of a
compact manifold with nonempty boundary, then the quotient of A_0 by the normal
subgroup of diffeomorphisms that coincide with the identity near to a given end
e of M is simple.Comment: This version corrects an error regarding the diffeomorphism groups of
R^1, since the line has two ends, in contrast to higher dimension
A least-squares implicit RBF-FD closest point method and applications to PDEs on moving surfaces
The closest point method (Ruuth and Merriman, J. Comput. Phys.
227(3):1943-1961, [2008]) is an embedding method developed to solve a variety
of partial differential equations (PDEs) on smooth surfaces, using a closest
point representation of the surface and standard Cartesian grid methods in the
embedding space. Recently, a closest point method with explicit time-stepping
was proposed that uses finite differences derived from radial basis functions
(RBF-FD). Here, we propose a least-squares implicit formulation of the closest
point method to impose the constant-along-normal extension of the solution on
the surface into the embedding space. Our proposed method is particularly
flexible with respect to the choice of the computational grid in the embedding
space. In particular, we may compute over a computational tube that contains
problematic nodes. This fact enables us to combine the proposed method with the
grid based particle method (Leung and Zhao, J. Comput. Phys. 228(8):2993-3024,
[2009]) to obtain a numerical method for approximating PDEs on moving surfaces.
We present a number of examples to illustrate the numerical convergence
properties of our proposed method. Experiments for advection-diffusion
equations and Cahn-Hilliard equations that are strongly coupled to the velocity
of the surface are also presented
Scanning-electron-microscopy observations and mechanical characteristics of ion-beam-sputtered surgical implant alloys
An electron bombardment ion thruster was used as an ion source to sputter the surfaces of orthopedic prosthetic metals. Scanning electron microscopy photomicrographs were made of each ion beam textured surface. The effect of ion texturing an implant surface on its bond to bone cement was investigated. A Co-Cr-W alloy and surgical stainless steel were used as representative hard tissue implant materials to determine effects of ion texturing on bulk mechanical properties. Work was done to determine the effect of substrate temperature on the development of an ion textured surface microstructure. Results indicate that the ultimate strength of the bulk materials is unchanged by ion texturing and that the microstructure will develop more rapidly if the substrate is heated prior to ion texturing
Detecting Full N-Particle Entanglement in Arbitrarily High-Dimensional Systems with Bell-Type Inequality
We derive a set of Bell-type inequalities for arbitrarily high-dimensional
systems, based on the assumption of partial separability in the hybrid
local-nonlocal hidden variable model. Partially entangled states would not
violate the inequalities, and thus upon violation, these Bell-type inequalities
are sufficient conditions to detect the full -particle entanglement and
validity of the hybrid local-nonlocal hidden variable description.Comment: 6 page
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