Effect of swift heavy ion irradiation on surface resistance of DyBa2Cu3O7−δ thin films at microwave frequencies

We report the observation of a pronounced peak in surface resistance at microwave frequencies of 4.88 GHz and 9.55 GHz and its disappearance after irradiation with swift ions in laser ablated DyBa2Cu3O7−δ (DBCO) thin films. The measurements were carried out in zero field as well as in the presence of magnetic fields (up to 0.8 T). The films were irradiated using 90 MeV oxygen ions at Nuclear Science Centre, New Delhi at a fluence of 3 × 10^13 ions/cm2. Introduction of point defects and extended defects after irradiation suppresses the peak at 9.55 GHz whereas no suppression is observed at 4.88 GHz. These results and the vortex dynamics in the films at microwave frequencies before and after irradiation are discussed

Illusions of general relativity in Brans-Dicke gravity

Contrary to common belief, the standard tenet of Brans-Dicke theory reducing to general relativity when omega tends to infinity is false if the trace of the matter energy-momentum tensor vanishes. The issue is clarified in a new approach using conformal transformations. The otherwise unaccountable limiting behavior of Brans-Dicke gravity is easily understood in terms of the conformal invariance of the theory when the sources of gravity have radiation-like properties. The rigorous computation of the asymptotic behavior of the Brans-Dicke scalar field is straightforward in this new approach.Comment: 16 pages, LaTeX, to appear in Physical Review

Peak effect and its evolution with defect structure in YBa2Cu3O7-d thin films at microwave frequencies

The vortex dynamics in YBa2Cu3O7-d thin films have been studied at microwave frequencies. A pronounced peak in the surface resistance, Rs, is observed in these films at frequencies of 4.88 and 9.55 GHz for magnetic fields varying from 0.2 to 0.8 T. The peak is associated with an order-disorder transformation of the flux line lattice as the temperature or field is increased. The occurrence of the peak in Rs is crucially dependent on the depinning frequency, wp and on the nature and concentration of growth defects present in these films. Introduction of artificial defects by swift heavy ion irradiation with 200 MeV Ag ion at a fluence of 4x1010 ions/cm2 enhances wp and suppresses the peak at 4.88 GHz but the peak at 9.55 GHz remains unaffected. A second peak at lower temperature has also been observed at 9.55 GHz. This is related to twin boundaries from angular dependence studies of Rs. Based on the temperature variation of Rs, vortex phase diagrams have been constructed at 9.55 GHz.Comment: 8 pages, 4 figures Submitted to Physical Review

Cosmology With Non-Minimally Coupled K-Field

We consider non-minimally coupled (with gravity) scalar field with non-canonical kinetic energy. The form of the kinetic term is of Dirac-Born-Infeld (DBI) form.We study the early evolution of the universe when it is sourced only by the k-field, as well as late time evolution when both the matter and k-field are present. For the k-field, we have considered constant potential as well as potential inspired from Boundary String Field Theory (B-SFT). We show that it is possible to have inflationary solution in early time as well as late time accelerating phase. The solutions also exhibit attractor property in a sense that it does not depend on the initial conditions for a certain values of the parameters.Comment: 10 pages, Revtex style, 14 eps figures, to appear in General Relativity and Gravitatio

Power-law entropy-corrected HDE and NADE in Brans-Dicke cosmology

Considering the power-law corrections to the black hole entropy, which appear in dealing with the entanglement of quantum fields inside and outside the horizon, the holographic energy density is modified accordingly. In this paper we study the power-law entropy-corrected holographic dark energy in the framework of Brans-Dicke theory. We investigate the cosmological implications of this model in detail. We also perform the study for the new agegraphic dark energy model and calculate some relevant cosmological parameters and their evolution. {As a result we find that this model can provide the present cosmic acceleration and even the equation of state parameter of this model can cross the phantom line $w_D=-1$ provided the model parameters are chosen suitably}.Comment: 14 pages, 2 figure, accepted by IJT

Synergistic warm inflation

We consider an alternative warm inflationary scenario in which $n$ scalar fields coupled to a dissipative matter fluid cooperate to produce power--law inflation. The scalar fields are driven by an exponential potential and the bulk dissipative pressure coefficient is linear in the expansion rate. We find that the entropy of the fluid attains its asymptotic value in a characteristic time proportional to the square of the number of fields. This scenario remains nearly isothermal along the inflationary stage. The perturbations in energy density and entropy are studied in the long--wavelength regime and seen to grow roughly as the square of the scale factor. They are shown to be compatible with COBE measurements of the fluctuations in temperature of the CMB.Comment: 13 pages, Revtex 3 To be published in Physical Review

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Interacting Ricci Dark Energy with Logarithmic Correction

Motivated by the holographic principle, it has been suggested that the dark energy density may be inversely proportional to the area $A$ of the event horizon of the universe. However, such a model would have a causality problem. In this work, we consider the entropy-corrected version of the holographic dark energy model in the non-flat FRW universe and we propose to replace the future event horizon area with the inverse of the Ricci scalar curvature. We obtain the equation of state (EoS) parameter $\omega_{\Lambda}$, the deceleration parameter $q$ and $\Omega_D'$ in the presence of interaction between Dark Energy (DE) and Dark Matter (DM). Moreover, we reconstruct the potential and the dynamics of the tachyon, K-essence, dilaton and quintessence scalar field models according to the evolutionary behavior of the interacting entropy-corrected holographic dark energy model.Comment: 24 pages, accepted for publication in 'Astrophysics and Space Science, DOI:10.1007/s10509-012-1031-8

The accelerated scaling attractor solution of the interacting agegraphic dark energy in Brans-Dicke theory

We investigate the interacting agegraphic dark energy in Brans-Dicke theory and introduce a new series general forms of dark sector coupling. As examples, we select three cases involving a linear interaction form (Model I) and two nonlinear interaction form (Model II and Model III). Our conclusions show that the accelerated scaling attractor solutions do exist in these models. We also find that these interacting agegraphic dark energy modes are consistent with the observational data. The difference in these models is that nonlinear interaction forms give more approached evolution to the standard $\Lambda$CDM model than the linear one. Our work implies that the nonlinear interaction forms should be payed more attention.Comment: 9 pages, 10 figures, accepted in Eur. Phys. J.

Whole genome sequence analysis of NDM-1, CMY-4, and SHV-12 coproducing salmonella enterica serovar typhimurium isolated from a case of fatal burn wound infection

Salmonella species are frequently associated with gastrointestinal infections such as diarrhea. However, extraintestinal Salmonella infections, including burn infections, have been described. Here, we report the first case of a carbapenem-resistant and metallo-β-lactamase (New Delhi metallo-β-lactamase), extended-spectrum β-lactamase (SHV-12), and AmpC β-lactamase (CMY-4) coproducing Salmonella Typhimurium isolated from a fatal case of burn wound infection. The publication highlights the necessity for the rational use of antibiotics (particularly the rational use of last-resort antibiotics such as carbapenems) in hospitals and burn units, as well as the need for systematic screening of Salmonella spp. (including Salmonella enterica serovar Typhimurium) for resistance to carbapenem antibiotics