Improvement of the hot QCD pressure by the minimal sensitivity criterion

The principles of minimal sensitivity (PMS) criterion is applied to the perturbative free energy density, or pressure, of hot QCD, which include the $\sim g_s^6 \ln g_s$ and part of the $\sim g_s^6$ terms. Applications are made separately to the short- and long-distance parts of the pressure. Comparison with the lattice results, at low temperatures, shows that the resultant `` optimal'' approximants are substantially improved when compared to the $\bar{MS}$ results. In particular, for the realistic case of three quark flavors, the `` optimal'' approximants are comparable with the lattice results.Comment: 14 pages, 9 figures, LaTe

O mutualismo como forma de gestão de risco na agricultura.

A agricultura é, notadamente, uma atividade que apresenta grau elevado de risco. Fenômenos climáticos extremos, por exemplo, podem afetar, de forma negativa, a produtividade e a rentabilidade do setor. Para protegerem-se desse risco os produtores utilizam mecanismos que buscam mitigá-lo, dos quais o mutualismo é uma das formas mais antigas. Este artigo enfoca, de maneira analítica, as principais iniciativas dos produtores de criar, por meio de suas cooperativas, sociedades mútuas que os assegurem contra eventos aleatórios adversos

Broken-symmetry-adapted Green function theory of condensed matter systems:towards a vector spin-density-functional theory

The group theory framework developed by Fukutome for a systematic analysis of the various broken symmetry types of Hartree-Fock solutions exhibiting spin structures is here extended to the general many body context using spinor-Green function formalism for describing magnetic systems. Consequences of this theory are discussed for examining the magnetism of itinerant electrons in nanometric systems of current interest as well as bulk systems where a vector spin-density form is required, by specializing our work to spin-density-functional formalism. We also formulate the linear response theory for such a system and compare and contrast them with the recent results obtained for localized electron systems. The various phenomenological treatments of itinerant magnetic systems are here unified in this group-theoretical description.Comment: 17 page

Rates of neutrino conversion and decay in hot and dense QED plasma

Using a real-time formalism of equilibrium and nonequilibrium quantum-field theory, we derive the reaction-rate formula for neutrino-conversion ($\nu \to \nu'$) process and $\nu \bar{\nu}'$ annihilation process, which take place in a hot and dense QED plasma with background (anti)neutrinos out of equilibrium. Also derived is the formula for the inverse processes to the above ones. Using the hard-thermal-loop resummation scheme, we include the contribution from the coherent processes. The decay/production of a neutrino causes an evolution of its spatial distribution. A scheme for dealing with this evolution is presented. For the case of isotropic neutrino distribution, numerical computation is carried out for the parameter region of type-II super-nova explosion. Defferential reaction rate exhibits characteristic peak structure, which comes from the coherent processes. The contribution from the above processes to the decay or damping rate of a parent neutrino $\nu$ is also studied.Comment: 27 pages and 13 figure

Search for magnetic monopoles using proportional counters filled with helium gas

Slow magnetic monopoles in cosmic rays have been searched at sea level with the detector which consists of seven layers of proportional counters filled with a mixture of He + 20% CH4. The velocities and the energy losses of the incident particles are measured. The upper limit of flux for the monopoles in the velocity range of 1 x 0.001 Beta 4 x 0.001 is 2.78 x 10 to the minus 12th power square centimeters sr sec of 90% confidence level

Delocalized Quasiparticles in the Vortex State of an Overdoped High-Tc Superconductor Probed by 63Cu NMR

We report the spin Knight shift (K_s) and the nuclear spin-lattice relaxation rate (1/T_1) in the vortex state as a function of magnetic field (H) up to 28 T in the high-T_c superconductor TlSr_{2}CaCu_2O_{6.8} (T_c=68 K). At low temperatures well below T_{c}, both K_s and 1/T_1 measured around the middle point between two nearest vortices (saddle point) increase substantially with increasing field, which indicate that the quasiparticle states with an ungapped spectrum are extended outside the vortex cores in a d-wave superconductor. The density of states (DOS) around the saddle point is found to be \kappa N_0\sqrt{H/H_{c2}}, with \kappa=0.5\sim0.7 and N_0 being the normal-state DOS.Comment: 4 pages, 5 figures, to appear in Phys. Rev. Let

Saari's homographic conjecture for planar equal-mass three-body problem under a strong force potential

Donald Saari conjectured that the $N$-body motion with constant configurational measure is a motion with fixed shape. Here, the configurational measure $\mu$ is a scale invariant product of the moment of inertia $I=\sum_k m_k |q_k|^2$ and the potential function $U=\sum_{i<j} m_i m_j/|q_i-q_j|^\alpha$, $\alpha >0$. Namely, $\mu = I^{\alpha/2}U$. We will show that this conjecture is true for planar equal-mass three-body problem under the strong force potential $\sum_{i<j} 1/|q_i-q_j|^2$

Inflating and deflating the self: Sustaining motivational concerns through self-evaluation

The final publication is available at Elsevier via http://dx.doi.org/10.1016/j.jesp.2013.11.008 © 2014. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/The ways in which individuals think and feel about themselves play a significant role in guiding behavior across many domains in life. The current studies investigate how individuals may shift the positivity of self-evaluations in order to sustain their chronic or momentary motivational concerns. Specifically, we propose that more positive self-evaluations support eagerness that sustains promotion-focused concerns with advancement, whereas less positive self-evaluations support vigilance that sustains prevention-focused concerns with safety. The current studies provide evidence that self-evaluation inflation is associated with promotion concerns whereas self-evaluation deflation is associated with prevention concerns, whether regulatory focus is situationally manipulated (Studies 1, 2b, and 3) or measured as a chronic individual difference (Study 2a). Following regulatory focus primes, individuals in a promotion focus showed relatively greater accessibility of positive versus negative self-knowledge compared to individuals in a prevention focus (Study 1). In an ongoing performance situation, participants in a promotion focus reported higher self-esteem than participants in a prevention focus (Studies 2a and 2b). Finally, individuals in a promotion focus persisted longer on an anagram task when given an opportunity to focus on their strengths versus weaknesses, which was not the case for individuals in a prevention focus (Study 3). Across studies, the predicted interactions were consistently obtained, although sometimes the effects were stronger for promotion or prevention motivation. We discuss implications for existing models of the motives underlying self-evaluation.National Institute of Mental Health [grant 39429] to E. Tory HigginsSocial Sciences and Humanities Research Council of Canada (SSHRC) Insight Grant to Abigail A. Schole