1,747 research outputs found
Muon colliders and the non-perturbative dynamics of the Higgs boson
A muon collider operating in the TeV energy range can be an ideal s-channel
Higgs boson factory. This is especially true for a heavy Higgs boson. The
non-perturbative dynamical aspects of such a Higgs boson were recently
investigated with large N expansion methods at next to leading order, and
reveal the existence of a mass saturation effect. Even at strong coupling, the
Higgs resonance remains always below 1 TeV. However, if the coupling is strong
enough, the resonance becomes impossible to be detected.Comment: Contributed to the International Conference on Physics Potential and
Development of mumu Colliders, December 15-17, 1999, San Francisco, C
An exact solution of the five-dimensional Einstein equations with four-dimensional de Sitter-like expansion
We present an exact solution to the Einstein field equations which is Ricci
and Riemann flat in five dimensions, but in four dimensions is a good model for
the early vacuum-dominated universe.Comment: 6 pages; to appear in Journal of Mathematical Physics; v2: reference
3 correcte
Factorization in integrable systems with impurity
This article is based on recent works done in collaboration with M. Mintchev,
E. Ragoucy and P. Sorba. It aims at presenting the latest developments in the
subject of factorization for integrable field theories with a reflecting and
transmitting impurity.Comment: 7 pages; contribution to the XIVth International Colloquium on
Integrable systems, Prague, June 200
Efficient description of strongly correlated electrons with mean-field cost
We present an efficient approach to the electron correlation problem that is
well-suited for strongly interacting many-body systems, but requires only
mean-field-like computational cost. %which is based on orbital optimization of
electron pairs. The performance of our approach is illustrated for the
one-dimensional Hubbard model with periodic boundary conditions for different
chain lengths, and for the non-relativistic quantum chemical Hamiltonian
exploring the symmetric dissociation of the H hydrogen chain.Comment: 4 pages, 4 figure
Random magnetic field and quasi-particle transports in the mixed state of high T_{c} cuprates
By a singular gauge transformation, the quasi-particle transport in the mixed
state of high T_{c} cuprates is mapped into charge-neutral composite Dirac
fermion moving in short-range correlated random scalar and long-range
correlated vector potential. A fully quantum mechanical approach to
longitudinal and transverse thermal conductivities is presented. The
semi-classical Volovik effect is presented in a quantum mechanical way. The
quasi-particle scattering from the random magnetic field which was completely
missed in all the previous semi-classical approaches is the dominant scattering
mechanism at sufficiant high magnetic field. The implications for experiments
are discussed.Comment: 4+ pages, 1 figure. To appear in Phys. Rev. Let
Higher Order Evaluation of the Critical Temperature for Interacting Homogeneous Dilute Bose Gases
We use the nonperturbative linear \delta expansion method to evaluate
analytically the coefficients c_1 and c_2^{\prime \prime} which appear in the
expansion for the transition temperature for a dilute, homogeneous, three
dimensional Bose gas given by T_c= T_0 \{1 + c_1 a n^{1/3} + [ c_2^{\prime}
\ln(a n^{1/3}) +c_2^{\prime \prime} ] a^2 n^{2/3} + {\cal O} (a^3 n)\}, where
T_0 is the result for an ideal gas, a is the s-wave scattering length and n is
the number density. In a previous work the same method has been used to
evaluate c_1 to order-\delta^2 with the result c_1= 3.06. Here, we push the
calculation to the next two orders obtaining c_1=2.45 at order-\delta^3 and
c_1=1.48 at order-\delta^4. Analysing the topology of the graphs involved we
discuss how our results relate to other nonperturbative analytical methods such
as the self-consistent resummation and the 1/N approximations. At the same
orders we obtain c_2^{\prime\prime}=101.4, c_2^{\prime \prime}=98.2 and
c_2^{\prime \prime}=82.9. Our analytical results seem to support the recent
Monte Carlo estimates c_1=1.32 \pm 0.02 and c_2^{\prime \prime}= 75.7 \pm 0.4.Comment: 29 pages, 3 eps figures. Minor changes, one reference added. Version
in press Physical Review A (2002
Unified theory of phase separation and charge ordering in doped manganite perovskites
A unified theory is developed to explain various types of electronic
collective behaviors in doped manganites RXMnO (R = La, Pr,Nd
etc. and X = Ca, Sr, Ba etc.). Starting from a realistic electronic model, we
derive an effective Hamiltonianis by ultilizing the projection perturbation
techniques and develop a spin-charge-orbital coherent state theory, in which
the Jahn-Teller effect and the orbital degeneracy of e electrons in Mn ions
are taken into account. Physically, the experimentally observed charge ordering
state and electronic phase separation are two macroscopic quantum phenomena
with opposite physical mechanisms, and their physical origins are elucidated in
this theory. Interplay of the Jahn-Teller effect, the lattice distortion as
well as the double exchange mechanism leads to different magnetic structures
and to different charge ordering patterns and phase separation.Comment: 10 ReVTEX pages with 4 figures attache
A simple necessary decoherence condition for a set of histories
Within the decoherent histories formulation of quantum mechanics, we
investigate necessary conditions for decoherence of arbitrarily long histories.
We prove that fine-grained histories of arbitrary length decohere for all
classical initial states if and only if the unitary evolution preserves
classicality of states (using a natural formal definition of classicality). We
give a counterexample showing that this equivalence does not hold for
coarse-grained histories.Comment: 11 pages,LaTe
Two-Staged Magnetoresistance Driven by Ising-like Spin Sublattice in SrCo6O11
A two-staged, uniaxial magnetoresistive effect has been discovered in
SrCo6O11 having a layered hexagonal structure. Conduction electrons and
localized Ising spins are in different sublattices but their interpenetration
makes the conduction electrons sensitively pick up the stepwise
field-dependence of magnetization. The stepwise field-dependence suggests two
competitive interlayer interactions between ferromagnetic Ising-spin layers,
i.e., a ferromagnetic nearest-layer interaction and an antiferromagnetic
next-nearest-layer interaction. This oxide offers a unique opportunity to study
nontrivial interplay between conduction electrons and Ising spins, the coupling
of which can be finely controlled by a magnetic field of a few Tesla.Comment: 14 pages, 4 figures, accepted for publication in Phys. Rev. Let
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