70,185 research outputs found
Symmetry limit properties of a priori mixing amplitudes for non-leptonic and weak radiative decays of hyperons
We show that the so-called parity-conserving amplitudes predicted in the a
priori mixing scheme for non-leptonic and weak radiative decays of hyperons
vanish in the strong-flavor symmetry limit
Structure and electronic properties of molybdenum monoatomic wires encapsulated in carbon nanotubes
Monoatomic chains of molybdenum encapsulated in single walled carbon
nanotubes of different chiralities are investigated using density functional
theory. We determine the optimal size of the carbon nanotube for encapsulating
a single atomic wire, as well as the most stable atomic arrangement adopted by
the wire. We also study the transport properties in the ballistic regime by
computing the transmission coefficients and tracing them back to electronic
conduction channels of the wire and the host. We predict that carbon nanotubes
of appropriate radii encapsulating a Mo wire have metallic behavior, even if
both the nanotube and the wire are insulators. Therefore, encapsulating Mo
wires in CNT is a way to create conductive quasi one-dimensional hybrid
nanostructures.Comment: 8 pages, 10 figure
The Kovacs effect in the one-dimensional Ising model: a linear response analysis
We analyze the so-called Kovacs effect in the one-dimensional Ising model
with Glauber dynamics. We consider small enough temperature jumps, for which a
linear response theory has been recently derived. Within this theory, the
Kovacs hump is directly related to the monotonic relaxation function of the
energy. The analytical results are compared with extensive Monte Carlo
simulations, and an excellent agreement is found. Remarkably, the position of
the maximum in the Kovacs hump depends on the fact that the true asymptotic
behavior of the relaxation function is different from the stretched exponential
describing the relevant part of the relaxation at low temperatures.Comment: accepted for publication in Phys. Rev.
Impact of dimerization and stretching on the transport properties of molybdenum atomic wires
We study the electrical and transport properties of monoatomic Mo wires with
different structural characteristics. We consider first periodic wires with
inter-atomic distances ranging between the dimerized wire to that formed by
equidistant atoms. We find that the dimerized case has a gap in the electronic
structure which makes it insulating, as opposed to the equidistant or
near-equidistant cases which are metallic. We also simulate two conducting
one-dimensional Mo electrodes separated by a scattering region which contains a
number of dimers between 1 and 6. The characteristics strongly depend on
the number of dimers and vary from ohmic to tunneling, with the presence of
different gaps. We also find that stretched chains are ferromagnetic.Comment: 8 pages, 7 figure
Destruction of Long-range Order by Quenching the Hopping Range in One Dimension
We study the dynamics in a one dimensional hard-core Bose gas with power-law
hopping after an abrupt reduction of the hopping range using the time-dependent
density-matrix renormalization group (t-DMRG) and bosonization techniques. In
particular, we focus on the destruction of the Bose-Einstein condensate (BEC),
which is present in the initial state in the thermodynamic limit. We argue that
this type of quench is akin to a sudden reduction in the effective
dimensionality of the system (from to ). We identify two
regimes in the evolution of the BEC fraction. For short times the decay of the
BEC fraction is Gaussian while for intermediate to long times, it is well
described by a stretched exponential with an exponent that depends on the
initial effective dimensionality of the system. These results are potentially
relevant for cold trapped-ion experiments which can simulate an equivalent of
hard-core bosons, i.e. spins, with tunable long-range interactions.Comment: 8 pages, 7 figures, accepted for publication in Phys. Rev.
Isolated vacua in supersymmetric Yang-Mills theories
An explicit proof of the existence of nontrivial vacua in the pure
supersymmetric Yang-Mills theories with higher orthogonal SO(N), N>=7 or the
G_2 gauge group defined on a 3-torus with periodic boundary conditions is
given. Extra vacuum states are separated by an energy barrier from the
perturbative vacuum A_i=0 and its gauge copies.Comment: 8 pages, no figures, late
- …