5,431 research outputs found
Anderson's "Theorem" and Bogoliubov-de Gennes Equations for Surfaces and Impurities
In order to incorporate spatial inhomogeneity due to nonmagnetic impurities,
Anderson [1] proposed a BCS-type theory in which single-particle states in such
an inhomogeneous system are used. We examine Anderson's proposal, in comparison
with the Bogoliubov-de Gennes equations, for the attractive Hubbard model on a
system with surfaces and impurities.
[1] P. W. Anderson, J. Phys. Chem. Solids {\bf 11}, 26 (1959).Comment: 2 pages, 2 figures, submitted to Physica C for M2S-HTSC-VI
Proceeding
A first search of excited states double beta and double electron capture decays of Pd110 and Pd102
A search for double beta decays of the palladium isotopes 110Pd and 102Pd
into excited states of their daughters was performed and first half-life limits
for the 2{\nu}{\beta}{\beta} and 0{\nu}{\beta}{\beta} decays into first excited
0+ and 2+ states of 5.89e19 yr and 4.40e19 yr (95% CL) for the 110Pd decay were
obtained. The half-life limits for the corresponding double electron capture
transition of 102Pd are 7.64e18 yr and 2.68e18 yr (95% CL) respectively. These
are the first measurements for 102Pd.Comment: Updated to published version. Refined analysis and minor text
changes. Half-life limits change
Strongly correlated hopping and many-body bound states
We study a system in which the quantum dynamics of electrons depend on the
particle density in their neighborhood. For any on-site repulsive interaction,
we show that the exact two-body and three-body ground states are bound states.
We also discuss the finite density case in a mean-field framework and we show
that the system can undergo an unusual transition from an effective attractive
interaction to a repulsive one, when varying the electron density.Comment: 6 pages, 6 EPS figures, minor modifications and references adde
Effective R-parity violation from supersymmetry breaking
We present a scenario in which Yukawa-like R-parity violating (RPV) couplings
are naturally suppressed. In our framework, RPV is assumed to originate from
the SUSY breaking mechanism and then transmitted into the SUSY Lagrangian only
through soft SUSY breaking operators in the scalar potential. The RPV
Yukawa-like operators of the superpotential, conventionally parametrized by the
couplings \lambda, \lambda' and \lambda'', are then generated through loops
containing the SUSY scalars, the gauginos and the soft RPV interactions and
are, therefore, manifest as effective operators with a typical strength of
order 10^{-3}.Comment: 4 pages, 2 figures, Revtex4. Main changes with respect to Version 1
are: improved discussions on RGE effects, discussion added on neutrino
masses, a toy model added for the proposed scenario. Conclusions remain
unchanged. As will appear in Phys. Rev.
Exact Bond-Located Spin Ground State in the Hubbard Chain with Off-Diagonal Coulomb Interactions
We show the existence of an exact ground state in certain parameter regimes
of one-dimensional half-filled extended Hubbard model with site-off-diagonal
interactions. In this ground state, the bond-located spin correlation exhibits
a long-range order. In the case when the spin space is SU(2) symmetric, this
ground state degenerates with higher spin states including a fully
ferromagnetic state. We also discuss the relation between the exact
bond-ordered ground state and the critical bond-spin-density-wave phase.Comment: 4 pages, 4 eps figure
Rigorous results on superconducting ground states for attractive extended Hubbard models
We show that the exact ground state for a class of extended Hubbard models
including bond-charge, exchange, and pair-hopping terms, is the Yang
"eta-paired" state for any non-vanishing value of the pair-hopping amplitude,
at least when the on-site Coulomb interaction is attractive enough and the
remaining physical parameters satisfy a single constraint. The ground state is
thus rigorously superconducting. Our result holds on a bipartite lattice in any
dimension, at any band filling, and for arbitrary electron hopping.Comment: 12 page
Improving Sequential Determinantal Point Processes for Supervised Video Summarization
It is now much easier than ever before to produce videos. While the
ubiquitous video data is a great source for information discovery and
extraction, the computational challenges are unparalleled. Automatically
summarizing the videos has become a substantial need for browsing, searching,
and indexing visual content. This paper is in the vein of supervised video
summarization using sequential determinantal point process (SeqDPP), which
models diversity by a probabilistic distribution. We improve this model in two
folds. In terms of learning, we propose a large-margin algorithm to address the
exposure bias problem in SeqDPP. In terms of modeling, we design a new
probabilistic distribution such that, when it is integrated into SeqDPP, the
resulting model accepts user input about the expected length of the summary.
Moreover, we also significantly extend a popular video summarization dataset by
1) more egocentric videos, 2) dense user annotations, and 3) a refined
evaluation scheme. We conduct extensive experiments on this dataset (about 60
hours of videos in total) and compare our approach to several competitive
baselines
Effects of Boson Dispersion in Fermion-Boson Coupled Systems
We study the nonlinear feedback in a fermion-boson system using an extension
of dynamical mean-field theory and the quantum Monte Carlo method. In the
perturbative regimes (weak-coupling and atomic limits) the effective
interaction among fermions increases as the width of the boson dispersion
increases. In the strong coupling regime away from the anti-adiabatic limit,
the effective interaction decreases as we increase the width of the boson
dispersion. This behavior is closely related with complete softening of the
boson field. We elucidate the parameters that control this nonperturbative
region where fluctuations of the dispersive bosons enhance the delocalization
of fermions.Comment: 14 pages RevTeX including 12 PS figure
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