1,597 research outputs found
Nonabelian Duality and Higgs Multiplets in Supersymmetric Grand Unified Theories
We consider strongly interacting supersymmetric gauge theories which break
dynamically the GUT symmetry and produce the light Higgs doublets naturally.
Two models we proposed in the previous articles are reanalyzed as two phases of
one theory and are shown to have desired features. Furthermore, employing
nonabelian duality proposed recently by Seiberg, we study the dual theory of
the above one and show that the low-energy physics of the original and dual
models are the same as expected. We note that the Higgs multiplets in the
original model are regarded as composite states of the elementary hyperquarks
in its dual theory. Theories with other hypercolors and similar matter contents
are also analyzed in the same way.Comment: 16 pages, LaTeX, no figur
Dimensional tuning of electronic states under strong and frustrated interactions
We study a model of strongly interacting spinless fermions on an anisotropic
triangular lattice. At half-filling and the limit of strong repulsive
nearest-neighbor interactions, the fermions align in stripes and form an
insulating state. When a particle is doped, it either follows a one-dimensional
free motion along the stripes or fractionalizes perpendicular to the stripes.
The two propagations yield a dimensional tuning of the electronic state. We
study the stability of this phase and derive an effective model to describe the
low-energy excitations. Spectral functions are presented which can be used to
experimentally detect signatures of the charge excitations.Comment: 4pages 4figures included. to appear in Phys. Rev. Lett. vol. 10
Ferromagnetism and orbital order in the two-orbital Hubbard model
We investigate spin and orbital states of the two-orbital Hubbard model on a
square lattice by using a variational Monte Carlo method at quarter-filling,
i.e., the electron number per site is one. As a variational wave function, we
consider a Gutzwiller projected wave function of a mean-field type wave
function for a staggered spin and/or orbital ordered state. Then, we evaluate
expectation value of energy for the variational wave functions by using the
Monte Carlo method and determine the ground state. In the strong Coulomb
interaction region, the ground state is the perfect ferromagnetic state with
antiferro-orbital (AF-orbital) order. By decreasing the interaction, we find
that the disordered state becomes the ground state. Although we have also
considered the paramagnetic state with AF-orbital order, i.e., purely orbital
ordered state, and partial ferromagnetic states with and without AF-orbital
order, they do not become the ground state.Comment: 4 pages, 1 figure, accepted for publication in Journal of Physics:
Conference Serie
Composability and Generalized Entropy
We address in this paper how tightly the composability nature of systems:
constrains definition of generalized entropies and
investigate explicitly the composability in some ansatz of the entropy form.Comment: 16 pages, LATEX file. To be published in Phys. Lett.
Enhanced Kondo Effect in an Electron System Dynamically Coupled with Local Optical Phonon
We discuss Kondo behavior of a conduction electron system coupled with local
optical phonon by analyzing the Anderson-Holstein model with the use of a
numerical renormalization group (NRG) method. There appear three typical
regions due to the balance between Coulomb interaction and
phonon-mediated attraction . For , we
observe the standard Kondo effect concerning spin degree of freedom. Since the
Coulomb interaction is effectively reduced as , the
Kondo temperature is increased when is increased. On
the other hand, for , there occurs the Kondo effect
concerning charge degree of freedom, since vacant and double occupied states
play roles of pseudo-spins. Note that in this case, is decreased
with the increase of . Namely, should be maximized for
. Then, we analyze in detail the Kondo behavior
at , which is found to be explained by the polaron
Anderson model with reduced hybridization of polaron and residual repulsive
interaction among polarons. By comparing the NRG results of the polaron
Anderson model with those of the original Anderson-Holstein model, we clarify
the Kondo behavior in the competing region of .Comment: 8 pages, 8 figure
Multipole State of Heavy Lanthanide Filled Skutterudites
We discuss multipole properties of filled skutterudites containing heavy
lanthanide Ln from a microscopic viewpoint on the basis of a seven-orbital
Anderson model. For Ln=Gd, in contrast to naive expectation, quadrupole moments
remain in addition to main dipole ones. For Ln=Ho, we find an exotic state
governed by octupole moment. For Ln=Tb and Tm, no significant multipole moments
appear at low temperatures, while for Ln=Dy, Er, and Yb, dipole and
higher-order multipoles are dominant. We briefly discuss possible relevance of
these multipole states with actual materials.Comment: 5 pages, 3 figure
Quantum Restoration of the U(1)_Y Symmetry in Dynamically Broken SUSY-GUT's
We propose a supersymmetric hypercolor SU(3)_H gauge theory interacting
strongly at the grand unification scale, in which the hyperquark condensation
breaks SU(5)_GUT down to SU(3)_C x SU(2)_L without unbroken U(1)_Y at the
classical level. However, we show that the broken U(1)_Y symmetry is restored
by quantum mechanical effects and hence there remains the standard-model gauge
symmetry at the electroweak scale. The dynamics of the strong interactions also
produces naturally a pair of massless Higgs doublets. In addition to these
Higgs doublets, we have a pair of massless singlets which contributes to the
renormalization-group equations of gauge coupling constants and hence affects
the GUT unification. We discuss a simple solution to this problem.Comment: 12 pages, LaTeX, 1 Postscript figur
K*-couplings for the antidecuplet excitation
We estimate the coupling of the K* vector meson to the N-->Theta+ transition
employing unitary symmetry, vector meson dominance, and results from the GRAAL
Collaboration for eta photoproduction off the neutron. Our small numerical
value for the coupling constant is consistent with the non-observation of the
Theta+ in recent CLAS searches for its photoproduction. We also estimate the
K*-coupling for the N-->Sigma* excitation, with Sigma* being the Sigma-like
antidecuplet partner of the Theta+-baryon.Comment: 9 pages, 1 figure. Minor changes in text and abstract, references
added; version to appear in Phys. Rev.
Spin-orbital gap of multiorbital antiferromagnet
In order to discuss the spin-gap formation in a multiorbital system, we
analyze an e_g-orbital Hubbard model on a geometrically frustrated zigzag chain
by using a density-matrix renormalization group method. Due to the appearance
of a ferro-orbital arrangement, the system is regarded as a one-orbital system,
while the degree of spin frustration is controlled by the spatial anisotropy of
the orbital. In the region of strong spin frustration, we observe a finite
energy gap between ground and first-excited states, which should be called a
spin-orbital gap. The physical meaning is clarified by an effective Heisenberg
spin model including correctly the effect of the orbital arrangement influenced
by the spin excitation.Comment: 8 pages, 6 figures, extended versio
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