Coupling hydrodynamics to nonequilibrium degrees of freedom in strongly interacting quark-gluon plasma

Relativistic hydrodynamics simulations of quark-gluon plasma play a pivotal role in our understanding of heavy ion collisions at RHIC and LHC. They are based on a phenomenological description due to Mueller, Israel, Stewart (MIS) and others, which incorporates viscous effects and ensures a well-posed initial value problem. Focusing on the case of conformal plasma we propose a generalization which includes, in addition, the dynamics of the least damped far-from-equilibrium degree of freedom found in strongly coupled plasmas through the AdS/CFT correspondence. We formulate new evolution equations for general flows and then test them in the case of N=4 super Yang-Mills plasma by comparing their solutions alongside solutions of MIS theory with numerical computations of isotropization and boost-invariant flow based on holography. In these tests the new equations reproduce the results of MIS theory when initialized close to the hydrodynamic stage of evolution, but give a more accurate description of the dynamics when initial conditions are set in the pre-equilibrium regime.Comment: Minor improvements; references adde

Hydrodynamic gradient expansion in gauge theory plasmas

We utilize the fluid-gravity duality to investigate the large order behavior of hydrodynamic gradient expansion of the dynamics of a gauge theory plasma system. This corresponds to the inclusion of dissipative terms and transport coefficients of very high order. Using the dual gravity description, we calculate numerically the form of the stress tensor for a boost-invariant flow in a hydrodynamic expansion up to terms with 240 derivatives. We observe a factorial growth of gradient contributions at large orders, which indicates a zero radius of convergence of the hydrodynamic series. Furthermore, we identify the leading singularity in the Borel transform of the hydrodynamic energy density with the lowest nonhydrodynamic excitation corresponding to a `nonhydrodynamic' quasinormal mode on the gravity side.Comment: v2: 4+2 pages, 2 figures, title changed by journal, supplemental material incorporated into the preprint, energy density coefficients up to 240th order included in the submission (change in normalization with respect to v1), matches published versio

Linearized nonequilibrium dynamics in nonconformal plasma

We investigate the behaviour of the lowest nonhydrodynamic modes in a class of holographic models which exhibit an equation of state closely mimicking the one determined from lattice QCD. We calculate the lowest quasinormal mode frequencies for a range of scalar self-interaction potentials and find that the damping of the quasinormal modes at the phase transition/crossover falls off by a factor of around two from conformality after factoring out standard conformal temperature dependence. The damping encoded in the imaginary part of the frequencies turns out to be correlated with the speed of sound and is basically independent of the UV details of the model. We also find that the dynamics of the nonhydrodynamic degrees of freedom remains ultralocal, even to a higher degree, as we deviate from conformality. These results indicate that the role of nonhydrodynamic degrees of freedom in the vicinity of the crossover transition may be enhanced

On the supergravity description of boost invariant conformal plasma at strong coupling

We study string theory duals of the expanding boost invariant conformal gauge theory plasmas at strong coupling. The dual supergravity background is constructed as an asymptotic late-time expansion, corresponding to equilibration of the gauge theory plasma. The absence of curvature singularities in the first few orders of the late-time expansion of the dual gravitational background unambiguously determines the equilibrium equation of the state, and the shear viscosity of the gauge theory plasma. While the absence of the leading pole singularities in the gravitational curvature invariants at the third order in late-time expansion determines the relaxation time of the plasma, the subleading logarithmic singularity can not be canceled within a supergravity approximation. Thus, a supergravity approximation to a dual description of the strongly coupled boost invariant expanding plasma is inconsistent. Nevertheless we find that the relaxation time determined from cancellation of pole singularities is quite robust.Comment: 26 pages, no figures; v2: references adde

The characteristics of thermalization of boost-invariant plasma from holography

We report on the approach towards the hydrodynamic regime of boost-invariant N=4 super Yang-Mills plasma at strong coupling starting from various far-from-equilibrium states at tau=0. The results are obtained through numerical solution of Einstein's equations for the dual geometries, as described in detail in the companion article arXiv:1203.0755. Despite the very rich far-from-equilibrium evolution, we find surprising regularities in the form of clear correlations between initial entropy and total produced entropy, as well as between initial entropy and the temperature at thermalization, understood as the transition to a hydrodynamic description. For 29 different initial conditions that we consider, hydrodynamics turns out to be definitely applicable for proper times larger than 0.7 in units of inverse temperature at thermalization. We observe a sizable anisotropy in the energy-momentum tensor at thermalization, which is nevertheless entirely due to hydrodynamic effects. This suggests that effective thermalization in heavy ion collisions may occur significantly earlier than true thermalization.Comment: 4 pages, 5 figures; see also the companion article arXiv:1203.0755; v2: figure corrected (fixes problem with Acrobat); v3: various clarifications and additional data points added; v4: typo fixed, publishe

A numerical relativity approach to the initial value problem in asymptotically Anti-de Sitter spacetime for plasma thermalization - an ADM formulation

This article studies a numerical relativity approach to the initial value problem in Anti-de Sitter spacetime relevant for dual non-equilibrium evolution of strongly coupled non-Abelian plasma undergoing Bjorken expansion. In order to use initial conditions for the metric obtained in arXiv:0906.4423 we introduce new, ADM formalism-based scheme for numerical integration of Einstein's equations with negative cosmological constant. The key novel element of this approach is the choice of lapse function vanishing at fixed radial position, enabling, if needed, efficient horizon excision. Various physical aspects of the gauge theory thermalization process in this setup have been outlined in our companion article arXiv:1103.3452. In this work we focus on the gravitational side of the problem and present full technical details of our setup. We discuss in particular the ADM formalism, the explicit form of initial states, the boundary conditions for the metric on the inner and outer edges of the simulation domain, the relation between boundary and bulk notions of time, the procedure to extract the gauge theory energy-momentum tensor and non-equilibrium apparent horizon entropy, as well as the choice of point for freezing the lapse. Finally, we comment on various features of the initial profiles we consider.Comment: 25 pages, 9 figures, 1 table; see also the companion article arXiv:1103.3452; v2: typos fixed; v3: references added and updated, publishe

Effects of Isotretinoin treatment on human body - review

Introduction: Isotretinoin (13-cis-Retinoic Acid) is a part of the retinoid group, and is used in dermatology for the treatment of acne, due to its demonstrated inhibitory effect on sebaceous gland activity and proliferation. Isotretinoin is a highly lipophilic drug, for this reason taking it with food, doubles the bioavailability of the substance, during systemic treatment. Isotretinoin as a drug has been used effectively for more than 40 years in the treatment of acne, although its exact mechanism of action is not known. Objective: The objective of this study is to gather and analyze literature regarding the adverse effects of isotretinoin therapy on mental health and the digestive, cardiovascular, immune, urinary, and reproductive systems. Materials and Methods: A literature review was conducted using the PubMed database with the following search terms : retinoids, isotretinoin, acne, 13-cis-retinoic acid. Current Knowledge: Isotretinoin therapy has a vast spectrum of side effects affecting various systems of the human body. During the use of isotretinoin, special caution should be taken in patients with depression, lipid disorders, and abnormal liver function. In addition, in patients of childbearing age, make sure to use contraception one month before, during and one month after the end of isotretinoin therapy due to its teratogenicity. Conclusion: Isotretinoin is still the most effective drug in the systemic treatment of severe forms of acne, nevertheless its potential side effects should be kept in mind. Regular monitoring of patients should be a mainstay during isotretinoin therapy, especially with regard to lipid profile and liver parameters

Glucagon-like peptide-1 receptor agonists and derivatives in the treatment of obesity - review

Abstract: Obesity is a chronic and insidious disease that represents a significant global. The World Health Organization has announced that almost 60% of European adults are overweight or obese. Complex hormonal and metabolic adaptations in obesity can prevent weight loss, despite changes in dietary and activity habits. Over the years, the number of anti-obesity drugs has been small and their efficacy has been inadequate, but powerful new drugs from the GLP-1 receptor agonists group have emerged. Studies indicate that drugs in the GLP-1 RA group can be effective in reducing weight in obese people both with and without diabetes. Several preparations are available on the market with varying efficacy and risk of side effects and new drugs are still being registered. Materials and Methods: Analysis of information on the treatment of obesity with GLP-1 receptor agonists using PubMed sources, including the epidemiology of obesity, types of GLP-1 RA drugs, their efficacy and safety. Aim: The aim of this publication was to gather the latest information on the treatment of obesity with GLP-1 receptor agonists. We wanted to present the epidemiology of obesity, the types of drugs, their efficacy and safety. Conclusions: Obesity is a significant problem in today's world and affects more than half of European adults. Drugs that are GLP-1 receptor agonists can effectively bridge the gap between behavioural strategies and bariatric surgery. Studies indicate that treatment with GLP-1 RAs can lead to significant weight loss in overweight and obese individuals compared to placebo, and tirzepatide appears to have the greatest efficacy. Keywords: obesity, weight loss, GLP-1 receptor agonist, dual GLP-1/GIP receptor agonist, semaglutide, tirzepatide

Anti-inflammatory effects of selected dietary components on endometriosis - review

Background: Endometriosis is a chronic inflammatory disorder that is among the most common gynaecological problems in women of reproductive age. The disease involves the presence of endometrial tissue outside the uterus, which manifests as pelvic pain and infertility. The main theory for its development suggests that endometrial cells move into the abdominal cavity during menstruation and implant there. This process leads to an increase in inflammatory cells and increased concentrations of cytokines, chemokines and prostaglandins, resulting in chronic inflammation. Objective: The aim of this work is to analyse in detail the available studies on the anti-inflammatory effects of selected dietary components such as polyphenols, vitamin D and omega-3 fatty acids. The work aims to evaluate their potential as future therapeutic options for the treatment of endometriosis, with a critical approach to their efficacy and possible application in the treatment of this disease.Materials and methods: A review of the literature available in the PubMed database was conducted using the following phrases in English: endometriosis, pain, diet, polyphenols, resveratrol, curcumin, vitamin D3, OMEGA-3 acids, polyunsaturated acidsState of knowledge: Changing dietary patterns in patients with endometriosis may result in a reduction in levels of inflammatory markers, which are typically elevated in this disease. Polyphenols, such as resveratrol and curcumin, show anti-inflammatory effects and inhibit endometrial cell proliferation. Vitamin D3 shows anti-inflammatory effects and influences angiogenesis. Omega-3 fatty acids may reduce inflammation and endometrial proliferation.Conclusions: The literature review indicates that polyphenols, vitamin D3 and omega-3 fatty acids offer promising therapeutic properties for the treatment of endometriosis, with anti-inflammatory and proliferative, pain-relieving effects. Despite these promising results, further clinical trials are needed