36,377 research outputs found

### The intruder feature of 31Mg and the coexistence of many particle and many hole states

The low-lying level structure of $^{31}{\rm Mg}$ has been investigated by the
antisymmetrized molecular dynamics (AMD) plus generator coordinate method (GCM)
with the Gogny D1S force. It is shown that the N=20 magic number is broken and
the ground state has the pure neutron $2p3h$ configuration. The coexistence of
many particle and many hole states at very low excitation energy is discussed

### Spontaneous Z2 Symmetry Breaking in the Orbifold Daughter of N=1 Super Yang-Mills Theory, Fractional Domain Walls and Vacuum Structure

We discuss the fate of the Z2 symmetry and the vacuum structure in an
SU(N)xSU(N) gauge theory with one bifundamental Dirac fermion. This theory can
be obtained from SU(2N) supersymmetric Yang--Mills (SYM) theory by virtue of Z2
orbifolding. We analyze dynamics of domain walls and argue that the Z2 symmetry
is spontaneously broken. Since unbroken Z2 is a necessary condition for
nonperturbative planar equivalence we conclude that the orbifold daughter is
nonperturbatively nonequivalent to its supersymmetric parent. En route, our
investigation reveals the existence of fractional domain walls, similar to
fractional D-branes of string theory on orbifolds. We conjecture on the fate of
these domain walls in the true solution of the Z2-broken orbifold theory. We
also comment on relation with nonsupersymmetric string theories and
closed-string tachyon condensation.Comment: 37 pages, 7 figures. v2: various significant changes; revisions
explained in the introduction. Final version to appear in Phys.Rev.

### Anisotropic Electronic Structure of the Kondo Semiconductor CeFe2Al10 Studied by Optical Conductivity

We report temperature-dependent polarized optical conductivity
[$\sigma(\omega)$] spectra of CeFe$_2$Al$_{10}$, which is a reference material
for CeRu$_2$Al$_{10}$ and CeOs$_2$Al$_{10}$ with an anomalous magnetic
transition at 28 K. The $\sigma(\omega)$ spectrum along the b-axis differs
greatly from that in the $ac$-plane, indicating that this material has an
anisotropic electronic structure. At low temperatures, in all axes, a shoulder
structure due to the optical transition across the hybridization gap between
the conduction band and the localized $4f$ states, namely $c$-$f$
hybridization, appears at 55 meV. However, the gap opening temperature and the
temperature of appearance of the quasiparticle Drude weight are strongly
anisotropic indicating the anisotropic Kondo temperature. The strong
anisotropic nature in both electronic structure and Kondo temperature is
considered to be relevant the anomalous magnetic phase transition in
CeRu$_2$Al$_{10}$ and CeOs$_2$Al$_{10}$.Comment: 5 pages, 4 figure

### Stochastic delocalization of finite populations

Heterogeneities in environmental conditions often induce corresponding
heterogeneities in the distribution of species. In the extreme case of a
localized patch of increased growth rates, reproducing populations can become
strongly concentrated at the patch despite the entropic tendency for population
to distribute evenly. Several deterministic mathematical models have been used
to characterize the conditions under which localized states can form, and how
they break down due to convective driving forces. Here, we study the
delocalization of a finite population in the presence of number fluctuations.
We find that any finite population delocalizes on sufficiently long time
scales. Depending on parameters, however, populations may remain localized for
a very long time. The typical waiting time to delocalization increases
exponentially with both population size and distance to the critical wind speed
of the deterministic approximation. We augment these simulation results by a
mathematical analysis that treats the reproduction and migration of individuals
as branching random walks subject to global constraints. For a particular
constraint, different from a fixed population size constraint, this model
yields a solvable first moment equation. We find that this solvable model
approximates very well the fixed population size model for large populations,
but starts to deviate as population sizes are small. The analytical approach
allows us to map out a phase diagram of the order parameter as a function of
the two driving parameters, inverse population size and wind speed. Our results
may be used to extend the analysis of delocalization transitions to different
settings, such as the viral quasi-species scenario

### Nonet meson properties in Nambu--Jona-Lasinio model with dimensional versus cutoff regularization

Nambu--Jona-Lasinio (NJL) model with Kobayashi-Maskawa-'t Hooft (KMT) term is
one of low energy effective theory of QCD which includes the $U_A(1)$ anomaly.
We investigate nonet meson properties in this model with three flavors of
quarks. We employ two type of regularizations the dimensional and sharp cutoff
ones. The model parameters are fixed phenomenologically for each
regularization. Evaluating the kaon decay constant, the $\eta$ meson mass and
the topological susceptibility, we show the regularization dependence of the
results and discuss the applicability of the NJL model.Comment: 11 pages, 9 figure

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