676 research outputs found
Temperature-extended Jarzynski relation: Application to the numerical calculation of the surface tension
We consider a generalization of the Jarzynski relation to the case where the
system interacts with a bath for which the temperature is not kept constant but
can vary during the transformation. We suggest to use this relation as a
replacement to the thermodynamic perturbation method or the Bennett method for
the estimation of the order-order surface tension by Monte Carlo simulations.
To demonstrate the feasibility of the method, we present some numerical data
for the 3D Ising model
The L1-Potts functional for robust jump-sparse reconstruction
We investigate the non-smooth and non-convex -Potts functional in
discrete and continuous time. We show -convergence of discrete
-Potts functionals towards their continuous counterpart and obtain a
convergence statement for the corresponding minimizers as the discretization
gets finer. For the discrete -Potts problem, we introduce an time
and space algorithm to compute an exact minimizer. We apply -Potts
minimization to the problem of recovering piecewise constant signals from noisy
measurements It turns out that the -Potts functional has a quite
interesting blind deconvolution property. In fact, we show that mildly blurred
jump-sparse signals are reconstructed by minimizing the -Potts functional.
Furthermore, for strongly blurred signals and known blurring operator, we
derive an iterative reconstruction algorithm
On the occurrence of oscillatory modulations in the power-law behavior of dynamic and kinetic processes in fractals
The dynamic and kinetic behavior of processes occurring in fractals with
spatial discrete scale invariance (DSI) is considered. Spatial DSI implies the
existence of a fundamental scaling ratio (b_1). We address time-dependent
physical processes, which as a consequence of the time evolution develop a
characteristic length of the form , where z is the dynamic
exponent. So, we conjecture that the interplay between the physical process and
the symmetry properties of the fractal leads to the occurrence of time DSI
evidenced by soft log-periodic modulations of physical observables, with a
fundamental time scaling ratio given by . The conjecture is
tested numerically for random walks, and representative systems of broad
universality classes in the fields of irreversible and equilibrium critical
phenomena.Comment: 6 pages, 3 figures. Submitted to EP
Measurement-Based Teleportation Along Quantum Spin Chains
We consider teleportation of an arbitrary spin-1/2 target quantum state along
the ground state of a quantum spin chain. We present a decomposition of the
Hilbert space of the many body quantum state into 4 vector spaces. Within each
of these subspaces, it is possible to take any superposition of states, and use
projective measurements to perform unit fidelity teleportation. Any such
superposition is necessarily a spin liquid state. We also show that all total
spin-0 quantum states belong in the same space, so that it is possible to
perform unit fidelity teleportation over any one-dimensional spin-0 many body
quantum state. We generalise to -Bell states, and present some general
bounds on fidelity of teleportation given a general state of a quantum spin
chain.Comment: 5 pages, 2 figures, presented as posters at "Quantum entanglement in
physical and information sciences", Pisa, 2004 and at the AIP Congress,
Canberra, 200
Diffusive Thermal Dynamics for the Ising Ferromagnet
We introduce a thermal dynamics for the Ising ferromagnet where the energy
variations occurring within the system exhibit a diffusive character typical of
thermalizing agents such as e.g. localized excitations. Time evolution is
provided by a walker hopping across the sites of the underlying lattice
according to local probabilities depending on the usual Boltzmann weight at a
given temperature. Despite the canonical hopping probabilities the walker
drives the system to a stationary state which is not reducible to the canonical
equilibrium state in a trivial way. The system still exhibits a magnetic phase
transition occurring at a finite value of the temperature larger than the
canonical one. The dependence of the model on the density of walkers realizing
the dynamics is also discussed. Interestingly the differences between the
stationary state and the Boltzmann equilibrium state decrease with increasing
number of walkers.Comment: 9 pages, 14 figures. Accepted for publication on PR
Dual Statistical Systems and Geometrical String
We analyse statistical system with interface energy proportional to the
length of the edges of interface. We have found the dual system high
temperature expansion of which equally well generates surfaces with linear
amplitude. These dual systems are in the same relation as 3D Ising ferromagnet
to the 3D Gauge spin system.Comment: 8 pages, Late
On the center of mass of Ising vectors
We show that the center of mass of Ising vectors that obey some simple
constraints, is again an Ising vector.Comment: 8 pages, 3 figures, LaTeX; Claims in connection with disordered
systems have been withdrawn; More detailed description of the simulations;
Inset added to figure
Thermal noise limitations to force measurements with torsion pendulums: Applications to the measurement of the Casimir force and its thermal correction
A general analysis of thermal noise in torsion pendulums is presented. The
specific case where the torsion angle is kept fixed by electronic feedback is
analyzed. This analysis is applied to a recent experiment that employed a
torsion pendulum to measure the Casimir force. The ultimate limit to the
distance at which the Casimir force can be measured to high accuracy is
discussed, and in particular the prospects for measuring the thermal correction
are elaborated upon.Comment: one figure, five pages, to be submitted to Phys Rev
Plasma fibrinogen: now also an antidepressant response marker?
Major depressive disorder (MDD) is one of the leading causes of global disability. It is a risk factor for noncompliance with medical treatment, with about 40% of patients not responding to currently used antidepressant drugs. The identification and clinical implementation of biomarkers that can indicate the likelihood of treatment response are needed in order to predict which patients will benefit from an antidepressant drug. While analyzing the blood plasma proteome collected from MDD patients before the initiation of antidepressant medication, we observed different fibrinogen alpha (FGA) levels between drug responders and nonresponders. These results were replicated in a second set of patients. Our findings lend further support to a recently identified association between MDD and fibrinogen levels from a large-scale study
- …