On the Role of Chaos in the AdS/CFT Connection

The question of how infalling matter in a pure state forms a Schwarzschild black hole that appears to be at non-zero temperature is discussed in the context of the AdS/CFT connection. It is argued that the phenomenon of self-thermalization in non-linear (chaotic) systems can be invoked to explain how the boundary theory, initially at zero temperature self thermalizes and acquires a finite temperature. Yang-Mills theory is known to be chaotic (classically) and the imaginary part of the gluon self-energy (damping rate of the gluon plasma) is expected to give the Lyapunov exponent. We explain how the imaginary part would arise in the corresponding supergravity calculation due to absorption at the horizon of the black hole.Comment: 18 pages. Latex file. Minor changes. Final version to appear in Modern Physics Letters

Light-front Schwinger Model at Finite Temperature

We study the light-front Schwinger model at finite temperature following the recent proposal in \cite{alves}. We show that the calculations are carried out efficiently by working with the full propagator for the fermion, which also avoids subtleties that arise with light-front regularizations. We demonstrate this with the calculation of the zero temperature anomaly. We show that temperature dependent corrections to the anomaly vanish, consistent with the results from the calculations in the conventional quantization. The gauge self-energy is seen to have the expected non-analytic behavior at finite temperature, but does not quite coincide with the conventional results. However, the two structures are exactly the same on-shell. We show that temperature does not modify the bound state equations and that the fermion condensate has the same behavior at finite temperature as that obtained in the conventional quantization.Comment: 10 pages, one figure, version to be published in Phys. Rev.

Effective Action of Spontaneously Broken Gauge Theories

The effective action of a Higgs theory should be gauge-invariant. However, the quantum and/or thermal contributions to the effective potential seem to be gauge-dependent, posing a problem for its physical interpretation. In this paper, we identify the source of the problem and argue that in a Higgs theory, perturbative contributions should be evaluated with the Higgs fields in the polar basis, not in the Cartesian basis. Formally, this observation can be made from the derivation of the Higgs theorem, which we provide. We show explicitly that, properly defined, the effective action for the Abelian Higgs theory is gauge invariant to all orders in perturbation expansion when evaluated in the covariant gauge in the polar basis. In particular, the effective potential is gauge invariant. We also show the equivalence between the calculations in the covariant gauge in the polar basis and the unitary gauge. These points are illustrated explicitly with the one-loop calculations of the effective action. With a field redefinition, we obtain the physical effective potential. The SU(2) non-Abelian case is also discussed.Comment: Expanded version, 32 pages, figures produced by LaTeX, plain LaTe

Behavior of logarithmic branch cuts in the self-energy of gluons at finite temperature

We give a simple argument for the cancellation of the log(-k^2) terms (k is the gluon momentum) between the zero-temperature and the temperature-dependent parts of the thermal self-energy.Comment: 4 page

Suite of simple metrics reveals common movement syndromes across vertebrate taxa

ecause empirical studies of animal movement are most-often site- and species-specific, we lack understanding of the level of consistency in movement patterns across diverse taxa, as well as a framework for quantitatively classifying movement patterns. We aim to address this gap by determining the extent to which statistical signatures of animal movement patterns recur across ecological systems. We assessed a suite of movement metrics derived from GPS trajectories of thirteen marine and terrestrial vertebrate species spanning three taxonomic classes, orders of magnitude in body size, and modes of movement (swimming, flying, walking). Using these metrics, we performed a principal components analysis and cluster analysis to determine if individuals organized into statistically distinct clusters. Finally, to identify and interpret commonalities within clusters, we compared them to computer-simulated idealized movement syndromes representing suites of correlated movement traits observed across taxa (migration, nomadism, territoriality, and central place foraging)

Real-time nonequilibrium dynamics in hot QED plasmas: dynamical renormalization group approach

We study the real-time nonequilibrium dynamics in hot QED plasmas implementing a dynamical renormalization group and using the hard thermal loop (HTL) approximation. The focus is on the study of the relaxation of gauge and fermionic mean fields and on the quantum kinetics of the photon and fermion distribution functions. For semihard photons of momentum eT << k << T we find to leading order in the HTL that the gauge mean field relaxes in time with a power law as a result of infrared enhancement of the spectral density near the Landau damping threshold. The dynamical renormalization group reveals the emergence of detailed balance for microscopic time scales larger than 1/k while the rates are still varying with time. The quantum kinetic equation for the photon distribution function allows us to study photon production from a thermalized quark-gluon plasma (QGP) by off-shell effects. We find that for a QGP at temperature T ~ 200 MeV and of lifetime 10 < t < 50 fm/c the hard (k ~ T) photon production from off-shell bremsstrahlung (q -> q \gamma and \bar{q} -> \bar{q}\gamma) at O(\alpha) grows logarithmically in time and is comparable to that produced from on-shell Compton scattering and pair annihilation at O(\alpha \alpha_s). Fermion mean fields relax as e^{-\alpha T t ln(\omega_P t)} with \omega_P=eT/3 the plasma frequency, as a consequence of the emission and absorption of soft magnetic photons. A quantum kinetic equation for hard fermions is obtained directly in real time from a field theoretical approach improved by the dynamical renormalization group. The collision kernel is time-dependent and infrared finite.Comment: RevTeX, 46 pages, including 5 EPS figures, published versio

'Let me take care of you': what can healthcare learn from a high-end restaurant to improve the patient experience?

Background: The patient experience is associated with patient satisfaction and health outcomes, presenting a key challenge in healthcare. The objective of the study was to explore the principles of care in and beyond healthcare, namely in a three Michelin-starred restaurant, and consider what, if any, principles of care from the diners’ experience could be transferrable to healthcare. Methods: The principles of care were first explored as part of observational fieldwork in a healthcare day surgery unit and restaurant respectively, focusing on communication between the professionals and the patients or the diners. Care was subsequently explored in a series of public engagement events across the UK. The events used immersive simulation to recreate the healthcare and the dining experiences for the general public, and to stimulate discussion. Results: A thematic analysis of the engagement discussions identified overarching themes in how care was experienced in and through communication; “informed, not bombarded”, “conversation, not interrogation”, “environment is communication”, and “being met as a person”. The themes suggested how the participants in simulation felt about the care they received in real time and provided recommendations for improved clinical practice. Conclusions: While practice improvements in healthcare are challenging, the patient experience could be enhanced by learning relational aspects of care from other sectors, including the high-end restaurant industry that focuses on meeting persons’ needs. Simulation provides a new kind of opportunity to bring professionals and patients together for focused discussions, prompted by immersive experiences of care and communication

Electromagnetic properties of a neutrino stream

In a medium that contains a neutrino background in addition to the matter particles, the neutrinos contribute to the photon self-energy as a result of the effective electromagnetic vertex that they acquire in the presence of matter. We calculate the contribution to the photon self-energy in a dense plasma, due to the presence of a gas of charged particles, or neutrinos, that moves as a whole relative to the plasma. General formulas for the transverse and longitudinal components of the photon polarization tensor are obtained in terms of the momentum distribution functions of the particles in the medium, and explicit results are given for various limiting cases of practical interest. The formulas are used to study the electromagnetic properties of a plasma that contains a beam of neutrinos. The transverse and longitudinal photon dispersion relations are studied in some detail. Our results do not support the idea that neutrino streaming instabilities can develop in such a system. We also indicate how the phenomenon of optical activity of the neutrino gas is modified due to the velocity of the neutrino background relative to the plasma. The general approach and results can be adapted to similar problems involving relativistic plasmas and high-temperature gauge theories in other environments.Comment: Revtex, 19 pages and 3 included ps file

The Plasmon in Hot ϕ4\phi^4 Theory

We study the 2-loop resummed propagator in hot $g^2\phi^4$ theory. The propagator has a cut along the whole real axis in the complex energy plane, but for small $g$, the spectral density is sharply peaked around the plasmon. The dispersion relation and the width of the plasmon are calculated at zero {\em and} finite momentum. At large momenta the spectral width vanishes, and the plasmon looses its collectivity and behaves like a non-interacting free particle.Comment: REVTeX, 30 pages, 8 uuencoded ps-figure