12,118 research outputs found

### Localization-delocalization transition in one-dimensional electron systems with long-range correlated disorder

We investigate localization properties of electron eigenstates in
one-dimensional (1d) systems with long-range correlated diagonal disorder.
Numerical studies on the localization length $\xi$ of eigenstates demonstrate
the existence of the localization-delocalization transition in 1d systems and
elucidate non-trivial behavior of $\xi$ as a function of the disorder strength.
The critical exponent $\nu$ for localization length is extracted for various
values of parameters characterizing the disorder, revealing that every $\nu$
disobeys the Harris criterion $\nu > 2/d$.Comment: 6 pages, 6 figuers, to be published in Phys. Rev.

### Molecular Hydrogen Emission from Protoplanetary Disks

We have modeled self-consistently the density and temperature profiles of gas
and dust in protoplanetary disks, taking into account irradiation from a
central star. Making use of this physical structure, we have calculated the
level populations of molecular hydrogen and the line emission from the disks.
As a result, we can reproduce the observed strong line spectra of molecular
hydrogen from protoplanetary disks, both in the ultraviolet (UV) and the
near-infrared, but only if the central star has a strong UV excess radiation.Comment: 19 pages, accepted for publication in Astronomy and Astrophysic

### Dimension-six Proton Decays in the Modified Missing Doublet SU(5) Model

Dimension-five operators for nucleon decays are suppressed in the modified
missing doublet (MMD) model in the supersymmetric SU(5) grand unification. We
show that nonrenormalizable interactions decrease the unification scale in the
MMD model which increases the nucleon decay rate of dimension-six operators by
a significant amount. We find that the theoretical lower bound on the proton
life time \tau(p \to \e^+ \pi^0) is within the observable range at
SuperKamiokande.Comment: 9 pages, Latex, 1 Postscript figure

### Bulk U(1) Messenger

We propose a new U(1) gauge interaction in the bulk in higher dimensional
spacetime, which transmits supersymmetry-breaking effects on the hidden brane
to the observable our brane. We find that rather small gauge coupling constant
of U(1)_{bulk}, $\alpha_{bulk} \simeq 5 \times 10^{-4}$, is required for a
successful phenomenology. This result implies the compactification length $L$
of the extra dimension to be $L^{-1} \simeq 2 \times 10^{15}GeV$ for
(4+1)-dimensional spacetime. This large compactification length $L$ is a
crucial ingredient to suppress unwanted flavor-changing neutral currents and
hence our proposal is very consistent with the Randall-Sundrum brane-world
scenario.Comment: 9 pages, Late

### Shape-phase transitions in odd-mass $\gamma$-soft nuclei with mass $A\approx 130$

Quantum phase transitions between competing equilibrium shapes of nuclei with
an odd number of nucleons are explored using a microscopic framework of nuclear
energy density functionals and a particle-boson core coupling model. The boson
Hamiltonian for the even-even core nucleus, as well as the spherical
single-particle energies and occupation probabilities of unpaired nucleons, are
completely determined by a constrained self-consistent mean-field calculation
for a specific choice of the energy density functional and pairing interaction.
Only the strength parameters of the particle-core coupling have to be adjusted
to reproduce a few empirical low-energy spectroscopic properties of the
corresponding odd-mass system. The model is applied to the odd-A Ba, Xe, La and
Cs isotopes with mass $A\approx 130$, for which the corresponding even-even Ba
and Xe nuclei present a typical case of $\gamma$-soft nuclear potential. The
theoretical results reproduce the experimental low-energy excitation spectra
and electromagnetic properties, and confirm that a phase transition between
nearly spherical and $\gamma$-soft nuclear shapes occurs also in the odd-A
systems.Comment: 13 pages, 15 figures, 9 table

### Signatures of shape phase transitions in odd-mass nuclei

Quantum phase transitions between competing ground-state shapes of atomic
nuclei with an odd number of protons or neutrons are investigated in a
microscopic framework based on nuclear energy density functional theory and the
particle-plus-boson-core coupling scheme. The boson-core Hamiltonian, as well
as the single-particle energies and occupation probabilities of the unpaired
nucleon, are completely determined by constrained self-consistent mean-field
calculations for a specific choice of the energy density functional and paring
interaction, and only the strength parameters of the particle-core coupling are
adjusted to reproduce selected spectroscopic properties of the odd-mass system.
We apply this method to odd-A Eu and Sm isotopes with neutron number $N \approx
90$, and explore the influence of the single unpaired fermion on the occurrence
of a shape phase transition. Collective wave functions of low-energy states are
used to compute quantities that can be related to quantum order parameters:
deformations, excitation energies, E2 transition rates and separation energies,
and their evolution with the control parameter (neutron number) is analysed.Comment: 15 pages, 13 figures; Accepted for publication in Phys. Rev.

### Surface density of states of s+-wave Cooper pairs in a two-band model

We calculate surface density of state (SDOS) of s+-wave Cooper pair in
two-band superconductor model, where gap functions have different signs between
two bands. We find that Andreev bound state appears at surface due to the sign
change in the gap function in the interband quasiparticle scattering. However,
we do not obtain the zero-energy peak of SDOS in contrast to the d-wave case.
The tunneling spectroscopy of s+-wave is much more complex as compared to the
d-wave case realized in high-Tc cuprates.Comment: 7 pages, 10 figure

### A Gauge Mediation Model of Dynamical Supersymmetry Breaking without Color Instability

We construct a gauge mediation model of dynamical supersymmetry breaking
(DSB) based on a vector-like gauge theory, in which there is a unique
color-preserving true vacuum. The DSB scale $\Lambda/4\pi$ turns out to be as
high as $\Lambda/4\pi \simeq 10^{8-9} GeV$, since the transmission of the DSB
effects to the standard model sector is completed through much higher loops.
This model is perfectly natural and phenomenologically consistent. We also
stress that the dangerous D-term problem for the messenger U(1)_m is
automatically solved by a charge conjugation symmetry in the vector-like gauge
theory.Comment: 11 pages, Late

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