745 research outputs found
Nonequilibrium spin transport on Au(111) surfaces
The well-known experimentally observed \textit{sp}-derived Au(111) Shockley
surface states with Rashba spin splitting are perfectly fit by an effective
tight-binding model, considering a two-dimensional hexagonal lattice with
-orbital and nearest neighbor hopping only. The extracted realistic band
parameters are then imported to perform the Landauer-Keldysh formalism to
calculate nonequilibrium spin transport in a two-terminal setup sandwiching a
Au(111) surface channel. Obtained results show strong spin density on the
Au(111) surface and demonstrate (i) intrinsic spin-Hall effect, (ii)
current-induced spin polarization, and (iii) Rashba spin precession, all of
which have been experimentally observed in semiconductor heterostructures, but
not in metallic surface states. We therefore urge experiments in the latter for
these spin phenomena.Comment: 5 pages, 3 figures, to be published in Phys. Rev.
Sonic crystal lenses that obey Lensmaker's formula
This paper presents a theoretical study of the phenomenon of acoustic imaging
by sonic crystals, which are made of two-dimensional regular arrays of rigid
cylinders placed in parallel in air. The scattering of acoustic waves is
computed using the standard multiple scattering theory, and the band structures
are computed by the plane-wave expansion method. It is shown that properly
arranged arrays not only can behave as acoustic lenses, but also the focusing
effect can be well described by Lensmaker's formula. Possible applications are
also discussed.Comment: 4 pages, 5 figure
Noncommutative Quantum Mechanics from Noncommutative Quantum Field Theory
We derive noncommutative multi-particle quantum mechanics from noncommutative
quantum field theory in the nonrelativistic limit. Paricles of opposite charges
are found to have opposite noncommutativity. As a result, there is no
noncommutative correction to the hydrogen atom spectrum at the tree level. We
also comment on the obstacles to take noncommutative phenomenology seriously,
and propose a way to construct noncommutative SU(5) grand unified theory.Comment: 14 pages, Latex, minor modification, references adde
Conformal Covariantization of Moyal-Lax Operators
A covariant approach to the conformal property associated with Moyal-Lax
operators is given. By identifying the conformal covariance with the second
Gelfand-Dickey flow, we covariantize Moyal-Lax operators to construct the
primary fields of one-parameter deformation of classical -algebras.Comment: 13 pages, Revtex, no figures, v.2: typos corrected, references added
and conclusion modifie
The BPS Domain Wall Solutions in Self-Dual Chern-Simons-Higgs Systems
We study domain wall solitons in the relativistic self-dual Chern-Simons
Higgs systems by the dimensional reduction method to two dimensional spacetime.
The Bogomolny bound on the energy is given by two conserved quantities in a
similar way that the energy bound for BPS dyons is set in some Yang-Mills-Higgs
systems in four dimensions. We find the explicit soliton configurations which
saturate the energy bound and their nonrelativistic counter parts. We also
discuss the underlying N=2 supersymmetry.Comment: 16 pages, LaTeX, no figure, a minor change in acknowledgment
Self-DUal SU(3) Chern-Simons Higgs Systems
We explore self-dual Chern-Simons Higgs systems with the local and
global symmetries where the matter field lies in the adjoint
representation. We show that there are three degenerate vacua of different
symmetries and study the unbroken symmetry and particle spectrum in each
vacuum. We classify the self-dual configurations into three types and study
their properties.Comment: Columbia Preprint CU-TP-635, 19 page
Cold Nuclear Matter In Holographic QCD
We study the Sakai-Sugimoto model of holographic QCD at zero temperature and
finite chemical potential. We find that as the baryon chemical potential is
increased above a critical value, there is a phase transition to a nuclear
matter phase characterized by a condensate of instantons on the probe D-branes
in the string theory dual. As a result of electrostatic interactions between
the instantons, this condensate expands towards the UV when the chemical
potential is increased, giving a holographic version of the expansion of the
Fermi surface. We argue based on properties of instantons that the nuclear
matter phase is necessarily inhomogeneous to arbitrarily high density. This
suggests an explanation of the "chiral density wave" instability of the quark
Fermi surface in large N_c QCD at asymptotically large chemical potential. We
study properties of the nuclear matter phase as a function of chemical
potential beyond the transition and argue in particular that the model can be
used to make a semi-quantitative prediction of the binding energy per nucleon
for nuclear matter in ordinary QCD.Comment: 31 pages, LaTeX, 1 figure, v2: some formulae corrected, qualitative
results unchange
Mass Spectra of N=2 Supersymmetric SU(n) Chern-Simons-Higgs Theories
An algebraic method is used to work out the mass spectra and symmetry
breaking patterns of general vacuum states in N=2 supersymmetric SU(n)
Chern-Simons-Higgs systems with the matter fields being in the adjoint
representation. The approach provides with us a natural basis for fields, which
will be useful for further studies in the self-dual solutions and quantum
corrections. As the vacuum states satisfy the SU(2) algebra, it is not
surprising to find that their spectra are closely related to that of angular
momentum addition in quantum mechanics. The analysis can be easily generalized
to other classical Lie groups.Comment: 17 pages, use revte
On the B\"acklund Transformation for the Moyal Korteweg-de Vries Hierarchy
We study the B\"acklund symmetry for the Moyal Korteweg-de Vries (KdV)
hierarchy based on the Kuperschmidt-Wilson Theorem associated with second
Gelfand-Dickey structure with respect to the Moyal bracket, which generalizes
the result of Adler for the ordinary KdV.Comment: 9 pages, Revte
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