8,916 research outputs found
Covariant gaussian approximation in Ginzburg - Landau model
Condensed matter systems undergoing second order transition away from the
critical fluctuation region are usually described sufficiently well by the mean
field approximation. The critical fluctuation region, determined by the
Ginzburg criterion, , is narrow even
in high superconductors and has universal features well captured by the
renormalization group method. However recent experiments on magnetization,
conductivity and Nernst effect suggest that fluctuations effects are large in a
wider region both above and below . In particular some "pseudogap"
phenomena and strong renormalization of the mean field critical temperature
can be interpreted as strong fluctuations effects that are
nonperturbative (cannot be accounted for by "gaussian fluctuations"). The
physics in a broader region therefore requires more accurate approach. Self
consistent methods are generally "non - conserving" in the sense that the Ward
identities are not obeyed. This is especially detrimental in the symmetry
broken phase where, for example, Goldstone bosons become massive. Covariant
gaussian approximation remedies these problems. The Green's functions obey all
the Ward identities and describe the fluctuations much better. The results for
the order parameter correlator and magnetic penetration depth of the Ginzburg -
Landau model of superconductivity are compared with both Monte Carlo
simulations and experiments in high cuprates.Comment: 24 pages, 7 figure
The Chern-Simons Coefficient in Supersymmetric Non-abelian Chern-Simons Higgs Theories
By taking into account the effect of the would be Chern-Simons term, we
calculate the quantum correction to the Chern-Simons coefficient in
supersymmetric Chern-Simons Higgs theories with matter fields in the
fundamental representation of SU(n). Because of supersymmetry, the corrections
in the symmetric and Higgs phases are identical. In particular, the correction
is vanishing for N=3 supersymmetric Chern-Simons Higgs theories. The result
should be quite general, and have important implication for the more
interesting case when the Higgs is in the adjoint representation.Comment: more references and explanation about rgularization dpendence are
included, 13 pages, 1 figure, latex with revte
SUSY QCD Corrections to Higgs Pair Production from Bottom Quark Fusion
We present a complete next-to-leading order (NLO) calculation for the total
cross section for inclusive Higgs pair production via bottom-quark fusion at
the CERN Large Hadron Collider (LHC) in the minimal supersymmetric standard
model (MSSM) and the minimal supergravity model (mSUGRA). We emphasize the
contributions of squark and gluino loops (SQCD) and the decoupling properties
of our results for heavy squark and gluino masses. The enhanced couplings of
the b quark to the Higgs bosons in supersymmetric models with large tanb yield
large NLO SQCD corrections in some regions of parameter space.Comment: 24 pages, 10 figure
Kaluza-Klein Induced Gravity Inflation
A D-dimensional induced gravity theory is studied carefully in a
dimensional Friedmann-Robertson-Walker space-time. We try to extract
information of the symmetry breaking potential in search of an inflationary
solution with non-expanding internal-space. We find that the induced gravity
model imposes strong constraints on the form of symmetry breaking potential in
order to generate an acceptable inflationary universe. These constraints are
analyzed carefully in this paper.Comment: 10 pages, title changed, corrected some typos, two additional
comments adde
Inflationary Universe in Higher Derivative Induced Gravity
In an induced-gravity model, the stability condition of an inflationary
slow-rollover solution is shown to be . The presence of higher derivative terms
will, however, act against the stability of this expanding solution unless
further constraints on the field parameters are imposed. We find that these
models will acquire a non-vanishing cosmological constant at the end of
inflation. Some models are analyzed for their implication to the early
universe.Comment: 6 pages, two typos correcte
Partial Wave Analysis of Scattering with Nonlocal Aharonov-Bohm Effect and Anomalous Cross Section induced by Quantum Interference
Partial wave theory of a three dmensional scattering problem for an arbitray
short range potential and a nonlocal Aharonov-Bohm magnetic flux is
established. The scattering process of a ``hard shere'' like potential and the
magnetic flux is examined. An anomalous total cross section is revealed at the
specific quantized magnetic flux at low energy which helps explain the
composite fermion and boson model in the fractional quantum Hall effect. Since
the nonlocal quantum interference of magnetic flux on the charged particles is
universal, the nonlocal effect is expected to appear in quite general potential
system and will be useful in understanding some other phenomena in mesoscopic
phyiscs.Comment: 6 figure
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
Nonmagnetic impurity perturbation to the quasi-two-dimensional quantum helimagnet LiCu2O2
A complete phase diagram of Zn substituted quantum quasi-two-dimensional
helimagnet LiCu2O2 has been presented. Helical ordering transition temperature
(T_h) of the original LiCu2O2 follows finite size scaling for less than ~ 5.5%
Zn substitution, which implies the existence of finite helimagnetic domains
with domain boundaries formed with nearly isolated spins. Higher Zn
substitution > 5.5% quenches the long-range helical ordering and introduces an
intriguing Zn level dependent magnetic phase transition with slight thermal
hysteresis and a universal quadratic field dependence for T_c (Zn > 0.055,H).
The magnetic coupling constants of nearest-neighbor (nn) J1 and
next-nearest-neighbor (nnn) J2 (alpha=J2/J1) are extracted from high
temperature series expansion (HTSE) fitting and N=16 finite chain exact
diagonalization simulation. We have also provided evidence of direct
correlation between long-range helical spin ordering and the magnitude of
electric polarization in this spin driven multiferroic material
Simulation of Dimensionally Reduced SYM-Chern-Simons Theory
A supersymmetric formulation of a three-dimensional SYM-Chern-Simons theory
using light-cone quantization is presented, and the supercharges are calculated
in light-cone gauge. The theory is dimensionally reduced by requiring all
fields to be independent of the transverse dimension. The result is a
non-trivial two-dimensional supersymmetric theory with an adjoint scalar and an
adjoint fermion. We perform a numerical simulation of this SYM-Chern-Simons
theory in 1+1 dimensions using SDLCQ (Supersymmetric Discrete Light-Cone
Quantization). We find that the character of the bound states of this theory is
very different from previously considered two-dimensional supersymmetric gauge
theories. The low-energy bound states of this theory are very ``QCD-like.'' The
wave functions of some of the low mass states have a striking valence
structure. We present the valence and sea parton structure functions of these
states. In addition, we identify BPS-like states which are almost independent
of the coupling. Their masses are proportional to their parton number in the
large-coupling limit.Comment: 18pp. 7 figures, uses REVTe
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