46,966 research outputs found
Integrable Magnetic Model of Two Chains Coupled by Four-Body Interactions
An exact solution for an XXZ chain with four-body interactions is obtained
and its phase diagram is determined. The model can be reduced to two chains
coupled by four-body interactions, and it is shown that the ground state of the
two-chain model is magnetized in part. Furthermore, a twisted four-body
correlation function of the anti-ferromagnetic Heisenberg chain is obtained.Comment: 7 pages, LaTeX, to be published in J. Phys. Soc. Jpn., rederived the
mode
Evidence for an Intense Neutrino Flux during -Process Nucleosynthesis?
We investigate the possibility that neutrino capture on heavy nuclei competes
with beta decay in the environment where the -Process elements are
synthesized. We find that such neutrino capture is not excluded by existing
abundance determinations. We show that inclusion of significant neutrino
capture on the (neutron number) N=82 waiting point nuclei can allow the
inferred abundances of these species to provide a good fit to steady weak (beta
decay plus neutrino capture) flow equilibrium. In fact, for particular choices
of neutrino flux conditions, this fit is improved over the case where nuclei
change their charge by beta decay alone. However, this improved fit can be
realized only if neutrino capture plays a negligible role in nuclear decay back
toward stability. We discuss the implications of these considerations for
current proposed sites and models for -Process nucleosynthesis.Comment: 10 pages, plain tex, submitted to ApJ
Correlated band structure of NiO, CoO and MnO by variational cluster approximation
The variational cluster approximation proposed by Potthoff is applied to the
calculation of the single-particle spectral function of the transition metal
oxides MnO, CoO and NiO. Trial self-energies and the numerical value of the
Luttinger-Ward functional are obtained by exact diagonalization of a
TMO6-cluster. The single-particle parameters of this cluster serve as
variational parameters to construct a stationary point of the grand potential
of the lattice system. The stationary point is found by a crossover procedure
which allows to go continuously from an array of disconnected clusters to the
lattice system. The self-energy is found to contain irrelevant degrees of
freedom which have marginal impact on the grand potential and which need to be
excluded to obtain meaningful results. The obtained spectral functions are in
good agreement with experimental data.Comment: 14 pages, 17 figure
Magnetic Phase Transitions in One-dimensional Strongly Attractive Three-Component Ultracold Fermions
We investigate the nature of trions, pairing and quantum phase transitions in
one-dimensional strongly attractive three-component ultracold fermions in
external fields. Exact results for the groundstate energy, critical fields,
magnetization and phase diagrams are obtained analytically from the Bethe
ansatz solutions. Driven by Zeeman splitting, the system shows exotic phases of
trions, bound pairs, a normal Fermi liquid and four mixtures of these states.
Particularly, a smooth phase transition from a trionic phase into a pairing
phase occurs as the highest hyperfine level separates from the two lower energy
levels. In contrast, there is a smooth phase transition from the trionic phase
into a normal Fermi liquid as the lowest level separates from the two higher
levels.Comment: 4 pages, 3 figures, minor revisions to text, replacement figure, refs
added and update
Quantum Spin Chains and Riemann Zeta Function with Odd Arguments
Riemann zeta function is an important object of number theory. It was also
used for description of disordered systems in statistical mechanics. We show
that Riemann zeta function is also useful for the description of integrable
model. We study XXX Heisenberg spin 1/2 anti-ferromagnet. We evaluate a
probability of formation of a ferromagnetic string in the anti-ferromagnetic
ground state in thermodynamics limit. We prove that for short strings the
probability can be expressed in terms of Riemann zeta function with odd
arguments.Comment: LaTeX, 7 page
On the center-vortex baryonic area law
We correct an unfortunate error in an earlier work of the author, and show
that in center-vortex QCD (gauge group SU(3)) the baryonic area law is the
so-called law, described by a minimal area with three surfaces spanning the
three quark world lines and meeting at a central Steiner line joining the two
common meeting points of the world lines. (The earlier claim was that this area
law was a so-called law, involving three extremal areas spanning the
three pairs of quark world lines.) We give a preliminary discussion of the
extension of these results to . These results are based on the
(correct) baryonic Stokes' theorem given in the earlier work claiming a
law. The -form area law for SU(3) is in agreement with the most
recent lattice calculations.Comment: 5 pages, RevTeX4, 5 .eps figure
Excited state TBA and functional relations in spinless Fermion model
The excited state thermodynamic Bethe ansatz (TBA) equations for the spinless
Fermion model are presented by the quantum transfer matrix (QTM) approach. We
introduce a more general family called T-functions and explore functional
relations among them (T-system) and their certain combinations (Y-system).
{}From their analytical property, we derive a closed set of non-linear integral
equations which characterize the correlation length of at
any finite temperatures. Solving these equations numerically, we explicitly
determine the correlation length, which coincides with earlier results with
high accuracy.Comment: 4 page
Spin-Wave Theory of the Spiral Phase of the t-J Model
A graded H.P,realization of the SU(2|1) algebra is proposed.A spin-wave
theory with a condition that the sublattice magnetization is zero is
discussed.The long-range spiral phase is investigated.The spin-spin correlator
is calculated.Comment: 17 page
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