51,279 research outputs found

### Chiral Lagrangian and spectral sum rules for dense two-color QCD

We analytically study two-color QCD with an even number of flavors at high
baryon density. This theory is free from the fermion sign problem. Chiral
symmetry is broken spontaneously by the diquark condensate. Based on the
symmetry breaking pattern we construct the low-energy effective Lagrangian for
the Nambu-Goldstone bosons. We identify a new epsilon-regime at high baryon
density in which the quark mass dependence of the partition function can be
determined exactly. We also derive Leutwyler-Smilga-type spectral sum rules for
the complex eigenvalues of the Dirac operator in terms of the fermion gap. Our
results can in principle be tested in lattice QCD simulations.Comment: 24 pages, 1 table, no figur

### Combined effect of frustration and dimerization in ferrimagnetic chains and square lattice

Within the zero-temperature linear spin-wave theory we have investigated the
effect of frustration and dimerization of a Heisenberg system with alternating
spins $s_{1}$ and $s_{2}$ on one- and two-dimensional lattices. The combined
effect most visibly appears in the elementary excitation spectra. In contrast
to the ground state energy that decreases with dimerization and increases with
frustration, the excitation energies are shown to be suppressed in energy by
both dimerization and frustration. The threshold value of frustration that
signals a transition from a classical ferrimagnetic state to a spiral state,
decreases with dimerization, showing that dimerization further helps in the
phase transition. The correlation length and sublattice magnetization decrease
with both dimerization and frustration indicating the destruction of the
long-range classical ferrimagnetic. The linear spin wave theory shows that in
the case of a square lattice, dimerization initially opposes the
frustration-led transition to a spiral magnetic state, but then higher
magnitudes of lattice deformation facilitate the transition. It also shows that
the transition to spiral state is inhibited in a square lattice beyond a
certain value of dimerization.Comment: 8 pages, latex, 12 postscript figure

### Spectral Continuity in Dense QCD

The vector mesons in three-flavor quark matter with chiral and diquark
condensates are studied using the in-medium QCD sum rules. The diquark
condensate leads to a mass splitting between the flavor-octet and
flavor-singlet channels. At high density, the singlet vector meson disappears
from the low-energy spectrum, while the octet vector mesons survive as light
excitations with a mass comparable to the fermion gap. A possible connection
between the light gluonic modes and the flavor-octet vector mesons at high
density is also discussed.Comment: 4 pages, 3 figures; version to appear in Phys. Rev.

### Ground State Property of an Alternating Spin Ladder Involving Two Kinds of Inter-Chain Interactions

The ground state property of the alternating spin ladder is studied in the
case that the system involves an antiferromagnetic intra-chain interaction as
well as two kinds of inter-chain interactions; one is between spins of the same
magnitude and the other is between spins with different magnitudes. The
calculation has been carried out by the exact diagonalization method. As a
consequence of the competition among interactions, the system is revealed to
show an interesting variety of phases in the ground state property. Its phase
diagram is exhibited in the parameter space of the system. We find that,
however small the total amount of the inter-chain interactions is, the
ferrimagnetic ground state becomes unstable in a certain region. In this case,
which of the ferrimagnetic and the singlet ground state to appear is determined
only by the ratio between the inter-chain interactions regardless of their
total amount. The nature of two phases appearing in the singlet region of the
phase diagram and the type of the phase transition between them are also
discussed. The results are ensured by comparing with those of obtained in other
models which are contained in our model as special limiting cases.Comment: 12 pages, 9 PostScript figure

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