20,043 research outputs found
Glide reflection symmetry, Brillouin zone folding and superconducting pairing for the space group
Motivated by the studies of the superconducting pairing states in the
iron-based superconductors, we analyze the effects of Brillouin zone folding
procedure from a space group symmetry perspective for a general class of
materials with the space group. The Brillouin zone folding amounts to
working with an effective one-Fe unit cell, instead of the crystallographic
two-Fe unit cell. We show that the folding procedure can be justified by the
validity of a glide reflection symmetry throughout the crystallographic
Brillouin zone and by the existence of a minimal double degeneracy along the
edges of the latter. We also demonstrate how the folding procedure fails when a
local spin-orbit coupling is included although the latter does not break any of
the space group symmetries of the bare Hamiltonian. In light of these general
symmetry considerations, we further discuss the implications of the glide
reflection symmetry for the superconducting pairing in an effective
multi-orbital model. We find that the space group
symmetry allows only pairing states with even parity under the glide reflection
and zero total momentum
Quasinormal Modes of Self-Dual Warped AdS Black Hole in Topological Massive Gravity
We consider the various perturbations of self-dual warped AdS black hole
and obtain the exact expressions of quasinormal modes by imposing the vanishing
Dirichlet boundary condition at asymptotic infinity. It is expected that the
quasinormal modes agree with the poles of retarded Green's functions of the
dual CFT. Our results provide a quantitative test of the warped AdS/CFT
correspondence.Comment: 10 pages, no figure, some references and comments on gravitational
perturbations are adde
An in-host model of HIV incorporating latent infection and viral mutation
We construct a seven-component model of the in-host dynamics of the Human
Immunodeficiency Virus Type-1 (i.e, HIV) that accounts for latent infection and
the propensity of viral mutation. A dynamical analysis is conducted and a
theorem is presented which characterizes the long time behavior of the model.
Finally, we study the effects of an antiretroviral drug and treatment
implications.Comment: 10 pages, 7 figures, Proceedings of AIMS Conference on Differential
Equations and Dynamical Systems (2015
A Tensor Approach to Learning Mixed Membership Community Models
Community detection is the task of detecting hidden communities from observed
interactions. Guaranteed community detection has so far been mostly limited to
models with non-overlapping communities such as the stochastic block model. In
this paper, we remove this restriction, and provide guaranteed community
detection for a family of probabilistic network models with overlapping
communities, termed as the mixed membership Dirichlet model, first introduced
by Airoldi et al. This model allows for nodes to have fractional memberships in
multiple communities and assumes that the community memberships are drawn from
a Dirichlet distribution. Moreover, it contains the stochastic block model as a
special case. We propose a unified approach to learning these models via a
tensor spectral decomposition method. Our estimator is based on low-order
moment tensor of the observed network, consisting of 3-star counts. Our
learning method is fast and is based on simple linear algebraic operations,
e.g. singular value decomposition and tensor power iterations. We provide
guaranteed recovery of community memberships and model parameters and present a
careful finite sample analysis of our learning method. As an important special
case, our results match the best known scaling requirements for the
(homogeneous) stochastic block model
symmetries of the Ricci tensor of static space times with maximal symmetric transverse spaces
Static space times with maximal symmetric transverse spaces are classified
according to their Ricci collineations. These are investigated for
non-degenerate Ricci tensor (). It turns out that the
only collineations admitted by these spaces can be ten, seven, six or four.
Some new metrics admitting proper Ricci collineations are also investigated.Comment: 11 page
- …