6,109 research outputs found
Multiple-orifice throttle valve
Multiple-orifice throttle valve is not subject to cold welding in a vacuum environment and is compatible with strong oxidizing fluid. The valve is of all metal construction using simple components that do not slide or rotate and excludes static or dynamic seals
Piecewise contractions defined by iterated function systems
Let be Lipschitz contractions. Let
, and . We prove that for Lebesgue almost every
satisfying , the piecewise
contraction defined by is
asymptotically periodic. More precisely, has at least one and at most
periodic orbits and the -limit set is a periodic orbit of
for every .Comment: 16 pages, two figure
Field induced multiple order-by-disorder state selection in antiferromagnetic honeycomb bilayer lattice
In this paper we present a detailed study of the antiferromagnetic classical
Heisenberg model on a bilayer honeycomb lattice in a highly frustrated regime
in presence of a magnetic field. This study shows strong evidence of entropic
order-by-disorder selection in different sectors of the magnetization curve.
For antiferromagnetic couplings , we find that at low
temperatures there are two different regions in the magnetization curve
selected by this mechanism with different number of soft and zero modes. These
regions present broken symmetry and are separated by a not fully
collinear classical plateau at . At higher temperatures, there is a
crossover from the conventional paramagnet to a cooperative magnet. Finally, we
also discuss the low temperature behavior of the system for a less frustrated
region, .Comment: revised version - accepted for publication in Physical Review B - 12
pages, 11 figure
Asymptotically periodic piecewise contractions of the interval
We consider the iterates of a generic injective piecewise contraction of the
interval defined by a finite family of contractions. Let , , be -diffeomorphisms with whose images are
pairwise disjoint. Let and let be a
partition of the interval into subintervals having interior
, where and . Let be the
map given by if , for . Among other
results we prove that for Lebesgue almost every , the
piecewise contraction is asymptotically periodic.Comment: 8 page
Reparametrization Invariance and the Schr\"odinger Equation
In the present work we consider a time-dependent Schr\"odinger equation for
systems invariant under the reparametrization of time. We develop the two-stage
procedure of construction such systems from a given initial ones, which is not
invariant under the time reparametrization. One of the first-class constraints
of the systems in such description becomes the time-dependent Schr\"odinger
equation. The procedure is applicable in the supersymmetric theories as well.
The supersymmetric quantum mechanics is coupled to world-line
supergravity, and the local supersymmetric action is constructed leading to the
square root representation of the time-dependent Schr\"odinger equation.Comment: RevTeX,25 page
Affine semigroups having a unique Betti element
We characterize affine semigroups having one Betti element and we compute
some relevant non-unique factorization invariants for these semigroups. As an
example, we particularize our description to numerical semigroups.Comment: 8 pages, 1 figure. To appear in Journal of Algebra and its
Application
Two repelling random walks on
We consider two interacting random walks on such that the
transition probability of one walk in one direction decreases exponentially
with the number of transitions of the other walk in that direction. The joint
process may thus be seen as two random walks reinforced to repel each other.
The strength of the repulsion is further modulated in our model by a parameter
. When both processes are independent symmetric
random walks on , and hence recurrent. We show that both random
walks are further recurrent if . We also show that these
processes are transient and diverge in opposite directions if . The
case remains widely open. Our results are obtained by
considering the dynamical system approach to stochastic approximations.Comment: 17 pages. Added references and corrected typos. Revised the argument
for the convergence to equilibria of the vector field. Improved the proof for
the recurrence when beta belongs to (0,1); leading to the removal of a
previous conjectur
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