Van der Waals black hole

In the context of extended phase space, where the negative cosmological constant is treated as a thermodynamic pressure in the first law of black hole thermodynamics, we find an asymptotically AdS metric whose thermodynamics matches exactly that of the Van der Waals fluid. However, we show that as a solution of Einstein's equations, the corresponding stress energy tensor does not obey any of the energy conditions everywhere outside of the horizon.Comment: 4 pages, 1 figure v3: corrected statements about energy condition

Lifshitz hydrodynamics at generic zz from a moving black brane

A Lifshitz black brane at generic dynamical critical exponent $z > 1$, with non-zero linear momentum along the boundary, provides a holographic dual description of a non-equilibrium steady state in a quantum critical fluid, with Lifshitz scale invariance but without boost symmetry. We consider moving Lifshitz branes in Einstein-Maxwell-Dilaton gravity and obtain the non-relativistic stress tensor complex of the dual field theory via a suitable holographic renormalisation procedure. The resulting black brane hydrodynamics and thermodynamics are a concrete holographic realization of a Lifshitz perfect fluid with a generic dynamical critical exponent.Comment: 18 page

Out-of-equilibrium hydrodynamics with and without boost symmetry

In this thesis, we explore the role of symmetries in hydrodynamics by studying certain properties of relativistic and non-relativistic fluids. In the first part of the thesis, we examine the theory of relativistic magnetohydrodynamics (Maxwell electromagnetism coupled to hydrodynamics) and its low temperature incarnation, force-free electrodynamics, reformulated in the language of higher-form symmetries and discuss the advantages of such a scheme. Using this framework, we analyse the regime of validity of force-free electrodynamics by evaluating the lifetime of the non-conserved electric field operator via a holographic model sharing the same global symmetries as that of a plasma. We are able to explicitly calculate the lifetime of the electric field, both parallel and perpendicular to the magnetic field, and find that there are indeed no long-lived modes that interfere with a hydrodynamic description of force-free electrodynamics. In the second part of the thesis, we study the thermodynamic properties of non-relativistic Lifshitz fluids with an arbitrary dynamic exponent z (encoding the anisotropy in the scaling of time and space coordinates). We study energy transport in such fluids far from equilibrium after performing a local quench between two semi-infinite fluid reservoirs. We find that the late time energy flow is universal and accommodated via a steady state occupying an expanding central region between outgoing shock and rarefaction waves (a non-equilibrium steady state), as seen previously for relativistic scale invariant fluids. Armed with an equation of state for a perfect Lifshitz fluid with an arbitrary z and moving with a velocity v, we proceed to study its holographic dual using the well established Einstein-Maxwell-Dilaton model. We find that the fluid velocity appears as the chemical potential, conjugate to the dual momentum density and the solutions represent a physically distinct class of black branes possessing a linear momentum, different from boosting a static brane

Non-equilibrium steady states in quantum critical systems with Lifshitz scaling

Publisher's version (útgefin grein).We study out-of-equilibrium energy transport in a quantum critical fluid with Lifshitz scaling symmetry following a local quench between two semi-infinite fluid reservoirs. The late time energy flow is universal and is accommodated via a steady state occupying an expanding central region between outgoing shock and rarefaction waves. We consider the admissibility and entropy conditions for the formation of such a non-equilibrium steady state for a general dynamical critical exponent z in arbitrary dimensions and solve the associated Riemann problem. The Lifshitz fluid with z = 2 can be obtained from a Galilean boost invariant field theory and the non-equilibrium steady state is identified as a boosted thermal state. A Lifshitz fluid with generic z is scale invariant but without boost symmetry and in this case the non-equilibrium steady state is genuinely non-thermal.This work was supported in part by the Icelandic Research Fund grant 195970- 051 and the University of Iceland Research Fund.Peer Reviewe

Opposing effects of cationic antimicrobial peptides and divalent cations on bacterial lipopolysaccharides

© 2017 American Physical SocietyThe permeability of the bacterial outer membrane, enclosing Gram-negative bacteria, depends on the interactions of the outer, lipopolysaccharide (LPS) layer, with surrounding ions and molecules. We present a coarse-grained model for describing how cationic amphiphilic molecules (e.g., antimicrobial peptides) interact with and perturb the LPS layer in a biologically relevant medium, containing monovalent and divalent salt ions (e.g., Mg2+). In our approach, peptide binding is driven by electrostatic and hydrophobic interactions and is assumed to expand the LPS layer, eventually priming it for disruption. Our results suggest that in parameter ranges of biological relevance (e.g., at micromolar concentrations) the antimicrobial peptide magainin 2 effectively disrupts the LPS layer, even though it has to compete with Mg2+ for the layer. They also show how the integrity of LPS is restored with an increasing concentration of Mg2+. Using the approach, we make a number of predictions relevant for optimizing peptide parameters against Gram-negative bacteria and for understanding bacterial strategies to develop resistance against cationic peptides.Natural Sciences and Engineering Research Council (NSERC) of Canad

Operator lifetime and the force-free electrodynamic limit of magnetised holographic plasma

Using the framework of higher-form global symmetries, we examine the regime of validity of force-free electrodynamics by evaluating the lifetime of the electric field operator, which is non-conserved due to screening effects. We focus on a holographic model which has the same global symmetry as that of low energy plasma and obtain the lifetime of (non-conserved) electric flux in a strong magnetic field regime. The lifetime is inversely correlated to the magnetic field strength and thus suppressed in the strong field regime

Phytochemical analysis, antioxidant, anti-inflammatory, anti-genotoxic, and anticancer activities of different Ocimum plant extracts prepared by ultrasound-assisted method

The genus Ocimum belonging to the family Lamiaceae, have been widely used in traditional medicines for the management of inflammation, dysentery, and chronic diarrhea as well as insect bites. The study aims to evaluate the phytochemistry and pharmacological activities of Ocimum gratissimum (OG), O. basilicum (OB), O. canum (OC), O. kilimandscharicum (OK), O. tenuiflorum (OT), and O. citriodorum (OXC) extracted in an ultrasound-assisted manner. There observed significantly higher polyphenols in OB (246.2 ± 8.0 mg GAE/g) and antioxidant activity in OG terms of DPPH radical (14.73 ± 0.54 μg/mL), ABTS+ radical and hydrogen peroxide scavenging assays (in OB with IC50 values 9.46 ± 0.28 and 6.22 ± 0.13 μg/mL); the most active extract was OB and OG. Similarly, OB, OG and OT were shown to have higher anti-inflammatory properties in terms of nitric oxide scavenging and lipoxygenase inhibition. Further, using the Allium cepa model, the genotoxicity of these extracts were evaluated; however, none of these plants was shown to have any kind of genotoxic potentials till a concentration of 500 μg/mL. Instead, they were able to protect the genotoxic effect of ethyl methyl sulfonate (EMS) in the dividing cells of Allium cepa. Further, these extracts, especially of OG, OT and OB, were found to reduce the proliferation of human breast cancer cells (OB and OC with IC50 values 49.36 ± 1.27 and 53.86 ± 0.96 μg/mL). The study identified the antioxidant, anti-inflammatory, anti-genotoxic and anticancer properties of ultrasound-assisted extracted Ocimum plants, with higher activity in OB and OG species.The authors acknowledge King Saud University, Riyadh, Saudi Arabia for funding this research through Researchers Supporting Project No: RSP 2021/11. The authors acknowledge KSCSTE for the student project scheme (No. 00784). AN and JTJ are thankful to DBT-STAR scheme and RUSA, Govt. of India for infrastructure development at St. Joseph's College (Autonomous), Devagiri.Peer reviewe