Conductivity of higher dimensional holographic superconductors with nonlinear electrodynamics

We investigate analytically as well as numerically the properties of s-wave holographic superconductors in $d$-dimensional spacetime and in the presence of Logarithmic nonlinear electrodynamics. We study three aspects of these kind of superconductors. First, we obtain, by employing analytical Sturm-Liouville method as well as numerical shooting method, the relation between critical temperature and charge density, $\rho$, and disclose the effects of both nonlinear parameter $b$ and the dimensions of spacetime, $d$, on the critical temperature $T_c$. We find that in each dimension, $T_c/{\rho}^{1/(d-2)}$ decreases with increasing the nonlinear parameter $b$ while it increases with increasing the dimension of spacetime for a fixed value of $b$. Then, we calculate the condensation value and critical exponent of the system analytically and numerically and observe that in each dimension, the condensation get larger with increasing the nonlinear parameter $b$. Besides, for a fixed value of $b$, it increases with increasing the spacetime dimension. We confirm that the results obtained from our analytical method are in agreement with the results obtained from numerical shooting method. This fact may support the correctness of our analytical method. Finally, we explore the holographic conductivity of this system and find out that the superconducting gap increases with increasing either the nonlinear parameter or the spacetime dimension.Comment: 25 page

Critical behaviour and microscopic structure of charged AdS black holes via an alternative phase space

It has been argued that charged Ads black holes have similar thermodynamic behavior as the Van der Waals fluid system, provided one treats the cosmological constant as a thermodynamic variable in an extended phase space. In this paper, we disclose the deep connection between charged AdS black holes and Van der Waals fluid system without extending the phase space. We keep the cosmological constant as a fixed parameter and instead, treat the square of the charge of black hole as a thermodynamic variable. Therefore, we write the equation of state as $Q^{2}=Q^{2}(T,\Psi)$ where $\Psi$ (conjugate of $Q^{2}$) is the inverse of the specific volume, $\Psi=1/v$. This allows us to complete the analogy of charged AdS black holes with Van der Waals fluid system and derive the phase transition as well as critical exponents of the system. We identify a thermodynamic instability in this new picture with real analogy to Van der Waals fluid with physically relevant Maxwell construction. We therefore study the critical behavior of isotherms in $$ diagram and deduce all the critical exponents of the system and determine that the system exhibits a small-large black hole phase transition at the critical point $(T_c,Q^2_c, \Psi_c)$. This alternative view is important as one can imagine such a change for a given single black hole i. e. acquiring charge which induces the phase transition. Finally, we disclose the microscopic properties of charged AdS black holes by using thermodynamic geometry. Interestingly, we find that scalar curvature has a gap between small and large black holes, and this gap becomes exceedingly large as one moves away from the critical point along the transition line. Therefore, we are able to attribute the sudden enlargement of the black hole to the strong repulsive nature of the internal constituents at the phase transition.Comment: 7 pages, 6 figures. New title and a new figure in the second versio

Microstructure of charged AdS black hole via P−VP-V criticality

We suggest a new thermodynamic curvature, constructed via adiabatic compressibility, for examining the internal microstructure of charged black holes in an anti-de Sitter (AdS) background. We analyze the microscopic properties of small-large phase transition of black holes with pressure and volume as the fluctuation variables. We observe that strong repulsive interactions dominate among the micro-structures of near extremal small black holes, and the thermodynamic curvature diverges to positive infinity for the extremal black holes. At the critical point, however, thermodynamic curvature diverges to negative infinity.Comment: 7 pages,4 figure

Universality class of alternative phase space and Van der Waals criticality

A new perspective toward thermodynamic phase space of Reisser-Nordstrom (RN) black holes in an anti-de-Sitter (AdS) spaces was recently proposed [Phys. Lett. B 768 (2017) 235], where the square of the electric charge $(Q^2)$ of black hole was regarded as a thermodynamic variable and the cosmological constant (pressure) as a fixed quantity. In this paper, we address the universality class and critical properties of any AdS black hole in this alternative phase space. We disclose the critical behavior of AdS black hole in the alternative phase space in which a continuous phase transition happens and in a very general framework, independent of the spacetime metric. Based on the expansion of the equation of state and Landau thermodynamic potential in the neighborhood of a critical point in the alternative phase space, we confirm that the set of values for critical exponents for generic black hole is analogous to the Van der Waals fluid system. Finally, we reveal that the scalar curvature in geometry thermodynamic diverges at the critical point of black hole. Our study shows that the approach here is powerful enough to investigate the critical behavior of any black holes and further supports the viability of the alternative viewpoint toward phase space of black holes suggested in [Phys. Lett. B 768 (2017) 235].Comment: 6 pages, two column

Burn Patients Infected With Metallo-Beta-Lactamase-Producing Pseudomonas aeruginosa: Multidrug-Resistant Strains

Background: Metallo-beta-lactamase (MBL) producing Pseudomonas aeruginosa in the burn patients is a leading cause of morbidity and mortality and remains a serious health concern among the clinicians. Objectives: The aim of this study was to detect MBL-producing P. aeruginosa in burn patients and determine multidrug-resistant (MDR) strains, and respective resistance patterns. Patients and Methods: In this cross-sectional study, 270 strains of P. aeruginosa were isolated from the burn patients referred to Ghotbeddin Burn Hospital, Shiraz, Iran. Among them, 55 MBL-producing P. aeruginosa strains were isolated from 55 patients hospitalized in burn unit. Minimum inhibitory concentrations (MICs) and MBLs were determined by the E-test method. Results: Of the 55 burn cases, 29 (53%) were females and 26 (47%) males. Injured burn patients’ ages ranged from 16 to 87 years, with maximum number of cases in the age group of 16 to 36 years (n, 40; 72.7%). Overall, 32 cases were accidental (60%), and 22 were suicidal burns (40%). Of the 55 burn patients, 17 cases were expired (30%). All deaths were due to chemical exposures. In antibiotic susceptibility testing by E-test method, ceftazidime was the most effective one and 35 isolates (63.5%) were resistant to all the 11 tested antibiotics. Conclusions: Routine microbiological surveillance and careful in vitro testing of antibiotics prior to prescription and strict adherence to hospital antibiotic policy may help to prevent, treat, and control MDR and pandrug-resistant (PDR) P. aeruginosa strains in burn units

Holographic conductivity of holographic superconductors with higher-order corrections

Abstract We analytically and numerically disclose the effects of the higher-order correction terms in the gravity and in the gauge field on the properties of s-wave holographic superconductors. On the gravity side, we consider the higher curvature Gauss–Bonnet corrections and on the gauge field side, we add a quadratic correction term to the Maxwell Lagrangian. We show that, for this system, one can still obtain an analytical relation between the critical temperature and the charge density. We also calculate the critical exponent and the condensation value both analytically and numerically. We use a variational method, based on the Sturm–Liouville eigenvalue problem for our analytical study, as well as a numerical shooting method in order to compare with our analytical results. For a fixed value of the Gauss–Bonnet parameter, we observe that the critical temperature decreases with increasing the nonlinearity of the gauge field. This implies that the nonlinear correction term to the Maxwell electrodynamics makes the condensation harder. We also study the holographic conductivity of the system and disclose the effects of the Gauss–Bonnet and nonlinear parameters $$\alpha$$ α and b on the superconducting gap. We observe that, for various values of $$\alpha$$ α and b, the real part of the conductivity is proportional to the frequency per temperature, $$\omega /T$$ ω/T , as the frequency is large enough. Besides, the conductivity has a minimum in the imaginary part which is shifted toward greater frequency with decreasing temperature

Characterization of multi-drug resistant ESBL producing nonfermenter bacteria isolated from patients blood samples using phenotypic methods in Shiraz (Iran)

Background and Aim: The emergence of  nonfermenter bacteria that are resistant to multidrug resistant ESBL  are  nowadays a principal problem  for hospitalized patients. The present study aimed at surveying the emergence of nonfermenter bacteria resistant to multi-drug ESBL producing isolated from patients blood samples using BACTEC 9240 automatic system in Shiraz. Materials and Methods: In this cross-sectional study, 4825 blood specimens were collected from hospitalized patients in Shiraz (Iran), and positive samples were detected by means of  BACTEC 9240 automatic system. The isolates  containing nonfermenter bacteria were identified based on biochemical tests embedded in the API-20E system. Antibiotic sensitivity  test was performed  and identification of  ESBL producing strains were done  using phenotypic detection of extended spectrum beta-lactamase producing isolates(DDST) according to CLSI(2013) guidelines.   Results: Out of 4825 blood samples, 1145 (24%) specimen were gram-positive using BACTEC system. Among all isolated microorganisms, 206 isolates were non-fermenting gram- negative bacteria. The most common non-fermenter isolates were Pseudomonas spp. (48%), Acinetobacter spp. (41.7%) ,and Stenotrophomonas spp. (8.2%). Seventy of them (81.4%) were  Acinetobacter spp. which were ESBL positive. Among &beta-lactam antibiotics, Pseudomonas spp. showed  the best sensitivity to piperacillin-tazobactam (46.5%).  Conclusion: It was found that  &beta-lactam antibiotics are not effective against more than 40% of Pseudomonas spp. infections and 78% Acinetobacter infections. Emergence of multi-drug resistant strains that are resistant to most antibiotic classes is a major public health problem in Iran. To resolve this problem using of practical guidelines is critical