118527348
Holographic superconductor/insulator transition with logarithmic electromagnetic field in Gauss–Bonnet gravity
Abstract The behaviors of the holographic superconductors/insulator transition are studied by introducing a charged scalar field coupled with a logarithmic electromagnetic field in both the Einstein–Gauss–Bonnet AdS black hole and soliton. For the Einstein–Gauss–Bonnet AdS black hole, we find that: i) the larger coupling parameter of logarithmic electrodynamic field b makes it easier for the scalar hair to be condensed; ii) the ratio of the gap frequency in conductivity ω g to the critical temperature T c depends on both b and the Gauss–Bonnet constant α; and iii) the critical exponents are independent of the b and α. For the Einstein–Gauss–Bonnet AdS soliton, we show that the system is the insulator phase when the chemical potential μ is small, but there is a phase transition and the AdS soliton reaches the superconductor (or superfluid) phase when μ is larger than critical chemical potential. A special property should be noted is that the critical chemical potential is not changed by the coupling parameter b but depends on α.
118567951
Phantom scalar emission in the Kerr black hole spacetime
We study the absorption probability and Hawking radiation spectra of a phantom scalar field in the Kerr black hole spacetime. We find that the presence of negative kinetic energy terms modifies the standard results in the graybody factor, super-radiance and Hawking radiation. Comparing with the usual scalar particle, the phantom scalar emission is enhanced in the black hole spacetime.
119285485
$P-V$ criticality of AdS black hole in $f(R)$ gravity
We study thermodynamics of a charged AdS black hole in the special $f(R)$ correction with the constant Ricci scalar curvature. Our results show that the the $f(R)$ correction influences the Gibbs free energy and the phase transition of system. The ratio $\rho_c$ occurred at the critical point increases monotonically with the derivative term $f'(R_0)$. We also disclose that the critical exponents are the same as those of the liquid-gas phase transition in the Van der Waals model, which does not depend on the $f(R)$ correction considered here.
118654249
Particle acceleration on the background of the Kerr―Taub―NUT spacetime
Abstract We study the collision of two particles with the different rest masses moving in the equatorial plane of a Kerr–Taub–NUT spacetime and get the center-of-mass (CM) energy for the particles. We find that the CM energy depends not only on the rotation parameter, a , but also on the NUT charge of the Kerr–Taub–NUT spacetime, n . Especially, for the extremal Kerr–Taub–NUT spacetime, an unlimited CM energy can be approached if the parameter a is in the range [ 1 , 2 ] , which is different from that of the Kerr and Kerr–Newman black holes.
119127372
Rotating charged black hole with Weyl corrections
We present firstly a four-dimensional spherical symmetric black hole with small Weyl corrections and find that with increasing Weyl corrections the region of the event horizon existence for the black hole in the parameter space increases for the negative Weyl coupling parameter and decreases for the positive one. Moreover, we also obtain a rotating charged black hole with weak Weyl corrections by the method of complex coordinate transformation. Our results show that the sign of Weyl coupling parameter $\alpha$ yields the different spatial topology of the event horizons for the black hole with its parameters lied in some special regions in the parameter space. We also analyze the dependence of the ergosphere on the Weyl coupling parameter $\alpha$ and find that with the increase of the Weyl corrections the ergosphere in the equatorial plane becomes thick for a black hole with $\alpha>0$, but becomes thin in the case with $\alpha<0$, which means that the energy extraction become easier in the background of a black hole with the positive Weyl coupling parameter, but more difficult in the background of a black hole with the negative one.
121869215
Dirac quasinormal modes of the Garfinkle-Horowitz-Strominger dilaton black-hole spacetime
Adopting the P?schl?Teller potential approximation, the quasinormal frequencies of the massless Dirac fields are evaluated in the Garfinkle?Horowitz?Strominger dilaton black-hole spacetime. We find that the real parts of the quasinormal frequencies increase as the orbital angular momentum k or a increases, where a is a parameter related to the dilaton field. The magnitude of imaginary parts decreases with k for the fixed a and overtone number n, while for fixed k and n, it is not a monotonic function of a and has a maximum at a point near a = 1.4?1.6, where the waves decay most rapidly. Another interesting feature is that the imaginary parts tend to zero and the real parts to k/2 as a approaches 2. We also find that the variation of the imaginary parts with the real parts in the Garfinkle?Horowitz?Strominger dilaton hole spacetimes is nonlinear, which becomes more complex than that in the Reissner?Nordstr?m black-hole spacetime.
2001409
Molecular organization of Gram-negative peptidoglycan
The stress-bearing component of the bacterial cell wall—a multi-gigadalton bag-like molecule called the sacculus—is synthesized from peptidoglycan. Whereas the chemical composition and the 3-dimensional structure of the peptidoglycan subunit (in at least one conformation) are known, the architecture of the assembled sacculus is not. Four decades' worth of biochemical and electron microscopy experiments have resulted in two leading 3-D peptidoglycan models: “Layered” and “Scaffold”, in which the glycan strands are parallel and perpendicular to the cell surface, respectively. Here we resolved the basic architecture of purified, frozen-hydrated sacculi through electron cryotomography. In the Gram-negative sacculus, a single layer of glycans lie parallel to the cell surface, roughly perpendicular to the long axis of the cell, encircling the cell in a disorganized hoop-like fashion.
117444261
The effect of high-order multipole imperfections on the LEP dynamic aperture
120967321
REPLY TO THE COMMENT ON "NONCOMMUTATIVITY AS A POSSIBLE ORIGIN OF THE ULTRAHIGH-ENERGY COSMIC RAY AND THE TEV PHOTON PARADOXES"
A cogitative comment on Ref. 1 was given by the author of Ref. 2 arguing that the Lorentz-noninvariant modification of the kinematic dispersion law does not follow from deformed oscillator systems, and it cannot evade ultrahigh energy threshold anomalies by raising the respective thresholds. It is pointed out that the dispersion relations of a q-deformed boson and fermion are derived heedlessly and further study on noncommutative theories is necessary. However if such dispersion relations are assumed tenable, the tachyonic propagation and photon instability do not exist at all because the deviation from 1 in q must be imaginary.
119228301
The big bang and inflation united by an analytic solution
Exact analytic solutions for a class of scalar-tensor gravity theories with a hyperbolic scalar potential are presented. Using an exact solution we have successfully constructed a model of inflation that produces the spectral index, the running of the spectral index, and the amplitude of scalar perturbations within the constraints given by the WMAP 7 years data. The model simultaneously describes the big bang and inflation connected by a specific time delay between them so that these two events are regarded as dependent on each other. In solving the Friedmann equations, we have utilized an essential Weyl symmetry of our theory in 3+1 dimensions which is a predicted remaining symmetry of 2T-physics field theory in 4+2 dimensions. This led to a new method of obtaining analytic solutions in the 1T field theory which could in principle be used to solve more complicated theories with more scalar fields. Some additional distinguishing properties of the solution includes the fact that there are early periods of time when the slow-roll approximation is not valid. Furthermore, the inflaton does not decrease monotonically with time; rather, it oscillates around the potential minimum while settling down, unlike the slow-roll approximation. While the model we used for illustrationmore » purposes is realistic in most respects, it lacks a mechanism for stopping inflation. The technique of obtaining analytic solutions opens a new window for studying inflation, and other applications, more precisely than using approximations.« less
119321899
Geodesically complete analytic solutions for a cyclic universe
We present analytic solutions to a class of cosmological models described by a canonical scalar field minimally coupled to gravity and experiencing self interactions through a hyperbolic potential. Using models and methods inspired by 2T-physics, we show how analytic solutions can be obtained in flat/open/closed Friedmann-Robertson-Walker universes. Among the analytic solutions, there are many interesting geodesically complete cyclic solutions in which the universe bounces at either zero or finite sizes. When geodesic completeness is imposed, it restricts models and their parameters to a certain parameter subspace, including some quantization conditions on initial conditions in the case of zero-size bounces, but no conditions on initial conditions for the case of finite-size bounces. We will explain the theoretical origin of our model from the point of view of 2T-gravity as well as from the point of view of the colliding branes scenario in the context of M-theory. We will indicate how to associate solutions of the quantum Wheeler-deWitt equation with our classical analytic solutions, mention some physical aspects of the cyclic solutions, and outline future directions.