18,748 research outputs found
The Klein first integrals in an equilibrium system with electromagnetic, weak, strong and gravitational interactions
The isothermal Tolman condition and the constancy of the Klein potentials
originally expressed for the sole gravitational interaction in a single fluid
are here generalized to the case of a three quantum fermion fluid duly taking
into account the strong, electromagnetic, weak and gravitational interactions.
The set of constitutive equations including the Einstein-Maxwell-Thomas-Fermi
equations as well as the ones corresponding to the strong interaction
description are here presented in the most general relativistic isothermal
case. This treatment represents an essential step to correctly formulate a
self-consistent relativistic field theoretical approach of neutron stars.Comment: To be published by Nuclear Physics
Noise effects in extended chaotic system: study on the Lorenz'96 model
We investigate the effects of a time-correlated noise on an extended chaotic
system. The chosen model is the Lorenz'96, a kind of toy model used for climate
studies. The system is subjected to both temporal and spatiotemporal
perturbations. Through the analysis of the system's time evolution and its time
correlations, we have obtained numerical evidence for two stochastic
resonance-like behaviors. Such behavior is seen when a generalized
signal-to-noise ratio function are depicted as a function of the external noise
intensity or as function of the system size. The underlying mechanism seems to
be associated to a noise-induced chaos reduction. The possible relevance of
those findings for an optimal climate prediction are discussed, using an
analysis of the noise effects on the evolution of finite perturbations and
errors.Comment: To appear in Statistical Mechanics Research Focus, Special volume
(Nova Science Pub., NY, in press) (LaTex, 16 pgs, 14 figures
The Logic & Limits of the Exceptional Circumstances Test in Magill and IMS Health
In this Article, we show that, in contrast to the Commission\u27s balancing approach in Microsoft, the ECJ\u27s narrow construction of the obligation to license IP under Article 82 of the EC Treaty is based on sound economics and constitutes appropriate public policy. The set of “exceptional circumstances” listed in Magill and IMS Health constitutes a reasonable implementation of the optimal legal standard for the assessment of refusals to licence IP: modified per se legality. In the IP context, an obligation to make property available is a requirement for compulsory licensing. The ECJ test limits compulsory licensing to those situations in which the prospective social benefits of licensing are large, while the negative effects of reducing the incentives to innovate are small. The ECJ test ensures that intervention is restricted to cases where the intervention is still likely to increase social welfare. The Commission\u27s test in Microsoft, being a balancing test, does not. As noted by Professor Gerardin, “balancing ex ante vs. ex post efficiencies is obviously a very difficult process, which even the most sophisticated economists may find daunting. The risk of mistaken decisions is therefore high.
The self-consistent general relativistic solution for a system of degenerate neutrons, protons and electrons in beta-equilibrium
We present the self-consistent treatment of the simplest, nontrivial,
self-gravitating system of degenerate neutrons, protons and electrons in
-equilibrium within relativistic quantum statistics and the
Einstein-Maxwell equations. The impossibility of imposing the condition of
local charge neutrality on such systems is proved, consequently overcoming the
traditional Tolman-Oppenheimer-Volkoff treatment. We emphasize the crucial role
of imposing the constancy of the generalized Fermi energies. A new approach
based on the coupled system of the general relativistic
Thomas-Fermi-Einstein-Maxwell equations is presented and solved. We obtain an
explicit solution fulfilling global and not local charge neutrality by solving
a sophisticated eigenvalue problem of the general relativistic Thomas-Fermi
equation. The value of the Coulomb potential at the center of the configuration
is and the system is intrinsically stable against
Coulomb repulsion in the proton component. This approach is necessary, but not
sufficient, when strong interactions are introduced.Comment: Letter in press, Physics Letters B (2011
Measuring the interaction force between a high temperature superconductor and a permanent magnet
Repulsive and attractive forces are both possible between a superconducting
sample and a permanent magnet, and they can give place to magnetic levitation
or free-suspension phenomena, respectively. We show experiments to quantify
this magnetic interaction which represents a promising field regarding to
short-term technological applications of high temperature superconductors. The
measuring technique employs an electronic balance and a rare-earth magnet that
induces a magnetic moment in a melt-textured YBa2Cu3O7 superconductor immersed
in liquid nitrogen. The simple design of the experiments allows a fast and easy
implementation in the advanced physics laboratory with a minimum cost. Actual
levitation and suspension demonstrations can be done simultaneously as a help
to interpret magnetic force measurements.Comment: 12 pages and 3 figures in postscrip
Ab initio Evidence for Giant Magnetoelectric Responses Driven by Structural Softness
We show that inducing structural softness in regular magnetoelectric (ME)
multiferroics -- i.e., tuning the materials to make their structure strongly
reactive to applied fields -- makes it possible to obtain very large ME
effects. We present illustrative first-principles results for BiFeO3 thin
films.Comment: 4 pages with 3 figures embedded. More information at
http://www.icmab.es/dmmis/leem/jorg
An Exact Approach to Early/Tardy Scheduling with Release Dates
In this paper we consider the single machine earliness/tardiness scheduling problem with di?erent release dates and no unforced idle time. The problem is decomposed into a weighted earliness subproblem and a weighted tardiness subproblem. Lower bounding procedures are proposed for each of these subproblems, and the lower bound for the original problem is then simply the sum of the lower bounds for the two subproblems. The lower bounds and several versions of a branch-and-bound algorithm are then tested on a set of randomly generated problems, and instances with up to 30 jobs are solved to optimality. To the best of our knowledge, this is the first exact approach for the early/tardy scheduling problem with release dates and no unforced idle time.scheduling, early/tardy, release dates, lower bounds, branch-and-bound
Diffusion in Fluctuating Media: The Resonant Activation Problem
We present a one-dimensional model for diffusion in a fluctuating lattice;
that is a lattice which can be in two or more states. Transitions between the
lattice states are induced by a combination of two processes: one periodic
deterministic and the other stochastic. We study the dynamics of a system of
particles moving in that medium, and characterize the problem from different
points of view: mean first passage time (MFPT), probability of return to a
given site (), and the total length displacement or number of visited
lattice sites (). We observe a double {\it resonant activation}-like
phenomenon when we plot the MFPT and as functions of the intensity of
the transition rate stochastic component.Comment: RevTex, 15 pgs, 8 figures, submitted to Eur.Phys.J.
Improved Lower Bounds for the Early/Tardy Scheduling Problem with No Idle Time
In this paper we consider the single machine earliness/tardiness scheduling problem with no idle time. Two of the lower bounds previously developed for this problem are based on lagrangean relaxation and the multiplier adjustment method, and require an initial sequence. We investigate the sensitivity of the lower bounds to the initial sequence, and experiment with di?erent dispatch rules and some dominance conditions. The computational results show that it is possible to obtain improved lower bounds by using a better initial sequence. The lower bounds are also incorporated in a branch-and-bound algorithm, and the computational tests show that one of the new lower bounds has the best performance for larger instances.scheduling, early/tardy, lower bound
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