The Dynamical Behaviour of Test Particles in?a?Quasi-spherical Spacetime and the?Physical Meaning?of?Superenergy

We calculate the instantaneous proper radial acceleration of test particles (as measured by a locally defined Lorentzian observer) in a Weyl spacetime, close to the horizon. As expected from the Israel theorem, there appear some bifurcations with respect to the spherically symmetric case (Schwarzschild) which are explained in terms of the behaviour of the superenergy, bringing out the physical relevance of this quantity in the study of general relativistic systems.     

Influence of Gauss-Bonnet Coupling Parameter on?the?Thermodynamic Properties of?Einstein-Gauss-Bonnet and?Einstein-Yang-Mills-Gauss-Bonnet Black Holes

This paper deals in the thermodynamic properties of Einstein-Gauss-Bonnet and Einstein-Yang-Mills-Gauss-Bonnet black holes. It exhibits the various stable and unstable phases of the black holes in these two modified gravity theories. In the first section, that reveals the various aspects of Einstein-Gauss-Bonnet black holes, we chose to study the changes in the Hawking Temperature with variations in the radius of event horizon (r) and charge (Q); and tried to justify them physically. Secondly in case of Einstein-Yang-Mills-Gauss-Bonnet black holes, we have attempted to compare the changes in the various thermodynamic parameters with varying r and Q; with the Einstein-Gauss-Bonnet black holes at a macroscopic level. Here we have considered the Yang Mills tensor, electromagnetic Lagrangian added to the action integrand. Again this very work deals in drawing out the similarities between these two types of black holes, thereby throwing some light on the aspect of black hole stability. Later we have also introspected the effects of the Gauss-Bonnet coupling parameter α, whose function (6αr), is added as a correction term to the black hole entropy. We have especially focused on what changes does it have upon the nature of the plots as to whether it enhances or reduces the effect of Q on the behavior of the curves. Finally this paper has also kept an eye at estimating the stability domains of the black holes described in these two gravity theories.     

Logic of discovery or psychology of invention?

It is noted that Popper separates the creation of concepts, conjectures, hypotheses and theories—the context of invention—from the testing thereof—the context of justification—arguing that only the latter is susceptible of rigorous logical analysis. Efforts on the part of others to shift or eradicate the demarcation established by this distinction are discussed and the relationship of these considerations to the claims of strong artificial intelligence is pointed out. It is argued that the mode of education of scientists, as well as reports of celebrated scientists, support Popper's judgement in this matter. An historical episode from Faraday's later career is used to illustrate the historiographical strength of Lakatos' methodology of research programs.     

Stars of strange matter?

We investigate suggestions that quark matter with strangeness per baryon of order unity may be stable. We model this matter at nuclear matter densities as a gas of close packed Λ-particles. From the known mass of the Λ-particle we obtain an estimate of the energy and chemical potential of strange matter at nuclear densities. These are sufficiently high to preclude any phase transition from neutron matter to strange matter in the region near nucleon matter density. Including effects from gluon exchange phenomenologically, we investigate higher densities, consistently making approximations which underestimate the density of transition. In this way we find a transition density ρ_tr≳7ρ₀, where ρ₀ is nuclear matter density is not far from the maximum density in the center of the most massive neutron stars that can be constructed. Since we have underestimated ρ_tr and still find it to be ∼7ρ₀, we do not believe that the transition from neutron to quark matter is likely in neutron stars. Moreover, measured masses of observed neutron stars are ≅1.4 M_⊙, where M_⊙ is the solar mass. For such masses, the central (maximum) density is ρ_c<5ρ₀. Transition to quark matter is certainly excluded for these densities.     

Thermodynamics Properties of the Inner Horizon of?a?Kerr-Newman Black Hole

In this paper, we study the thermal properties of the inner horizon of a Kerr-Newman black hole. By adopting Damour-Ruffini method and the thin film model which is developed on the base of brick wall model suggested by ’t Hooft, we calculate the temperature and the entropy of the inner horizon of a Kerr-Newman black hole. We conclude that the temperature of inner horizon is positive and the entropy of the inner horizon is proportional to the area of the inner horizon. The cut-off factor is same as it in calculation of the entropy of the outer horizon, 90β. In addition, we write the integral and differential Bekenstein-Smarr formula as the parameters of the inner horizon. Then, we discuss that if the contribution of the inner horizon is taken into account to the total entropy of the black hole, the Nernst theorem can be satisfied. At last, We calculate the tunneling rate of the outer horizon Γ₊ and the inner horizon Γ₋. The total tunneling rate Γ should be the product of the rates of the outer and inner horizon, Γ=Γ₊⋅Γ₋. We find that the total tunneling rate is in agreement with the Parikh’s standard result, Γ→exp (ΔS _BH ), and there is no information loss.     

Investigation of microstructure and?photo-magnetic properties of?sulfur-doped DLC nanocomposite films by?electrochemical method

Sulfur-doped DLC nanocomposite films have been successfully deposited by the electrochemical method using the mixture of methanol and thiofuran as the precursor at ambient atmospheric pressure. In contrast to DLC film, the effects of sulfur incorporation on the microstructural transformation and properties of sulfur-doped DLC nanocomposite films were investigated in detail in terms of atomic force microscopy, X-ray photoelectron spectroscopy, Raman spectrum and photoluminescence and magnetic tests. The experimental results showed that the unexpected organic molecular structure was formed like sulfone or thiols in sulfur-doped DLC nanocomposite films, and the concentration of sulfur in films was readily manipulated by the volume ratio of thiofuran to methanol. Meanwhile, the sp³-hybridized carbon content gradually decreased in films as the volume of thiofuran increased. Furthermore, sulfur-doped DLC nanocomposite films showed the monochromatic photoluminescence performance with a wide band centered at 510 nm, which could be attributed to carrier localization within an increasing sp² clusters and the defects along with the sulfur doping. Particularly, ferro-like magnetic performance of sulfur-doped DLC nanocomposite film might originate from the magnetic moment of localized sp² clusters with different charged carriers near the Fermi level after sulfur incorporation.     

Feynman’s Proof of Maxwell Equations: in?the?Context?of Quantum Gravity

Many of us are familiar with Feynman’s “proof” of 1948, as revealed by Dyson, which demonstrates that Maxwell equations of electromagnetism are a consequence of Newton’s laws of motion of classical mechanics and the commutation relations of coordinate and momentum of quantum mechanics. It was Feynman’s purpose to explore the universality of dynamics of particles while making the fewest assumptions. We re-examine this formulation in the context of quantum gravity and show how Feynman’s derivation can be extended to include quantum gravity.     

Wigner Function, Husimi Function and Tomogram of?Atomic?Coherent State as Energy Eigenstate of?Two?Coupled?Oscillators

In this work, we find that a set of energy eigenstates of the Hamiltonian of two coupled oscillators can be classified as the atomic coherent state in the Schwinger Bosonic realization. The statistical properties of these states are also discussed by analytically calculating their Wigner function, Husimi function and tomogram.     

Demise of the Cosmic Censor?

Initial data for general relativity may be such that there are trapped surfaces on a spatial initial data surface. Penrose has proposed that if the cosmic censorship hypothesis is true, the ADM mass M of asymptotically flat initial data and the area A of the outermost apparent horizon surface should satisfy the inequality A 16M². Initial data which does not satisfy this inequality may be viewed as providing a counterexample of the cosmic censorship conjecture. We describe initial data that appears to violate this inequality.     

Are citations of scientific papers a case of nonextensivity?

The distribution N(x) of citations of scientific papers has recently been illustrated (on ISI and PRE data sets) and analyzed by Redner (Eur. Phys. J. B 4, 131 (1998)). To fit the data, a stretched exponential () has been used with only partial success. The success is not complete because the data exhibit, for large citation count x, a power law (roughly for the ISI data), which, clearly, the stretched exponential does not reproduce. This fact is then attributed to a possibly different nature of rarely cited and largely cited papers. We show here that, within a nonextensive thermostatistical formalism, the same data can be quite satisfactorily fitted with a single curve (namely, [0pt] for the available values of x. This is consistent with the connection recently established by Denisov (Phys. Lett. A 235, 447 (1997)) between this nonextensive formalism and the Zipf-Mandelbrot law. What the present analysis ultimately suggests is that, in contrast to Redner's conclusion, the phenomenon might essentially be one and the same along the entire range of the citation number x. Received 13 April 1999     

Role of Brans-Dicke Theory with?or?without?Self-Interacting Potential in?Cosmic?Acceleration

In this work we have studied the possibility of obtaining cosmic acceleration in Brans-Dicke theory with varying or constant ω (Brans-Dicke parameter) and with or without self-interacting potential, the background fluid being barotropic fluid or Generalized Chaplygin Gas. Here we take the power law form of the scale factor and the scalar field. We show that accelerated expansion can also be achieved for high values of ω for closed Universe.     

Fabrication of silicon microwire arrays for?photovoltaic?applications

A?novel method of combining photolithography, wet chemical etching and oxidation process was proposed to fabricate large area of silicon microwire (SiMW) arrays. The dimensions of the SiMWs can be easily controlled by photomask and etching conditions. Solar cells based on the heterojunction between SiMW and double-walled carbon nanotubes (DWNTs) were constructed. The initial test on the DWNT/SiMW shows efficiency (??) of?0.59%. By adding a few drops of HBr/B₂ electrolyte, the efficiency was improved to 1.96% with J _sc=19.2?mA/cm² and V _oc=0.35?V, FF=29.2%, showing the potential of SiMWs in photovoltaic applications.     

Phenomenology of Λ-CDM Model: A?Possibility of?Accelerating Universe with Positive Pressure

Among various phenomenological Λ models, a time-dependent model [(L)\dot] ~ H³\dot{\Lambda}\sim H^{3} is selected here to investigate the Λ-CDM cosmology. The model can follow from dynamics, underlying the origin of Λ. Using this model the expressions for the time-dependent equation of state parameter ω and other physical parameters are derived. It is shown that in H ³ model accelerated expansion of the Universe takes place at negative energy density, but with a positive pressure. It has also been possible to obtain the change of sign of the deceleration parameter q during cosmic evolution.     

A confirmation of agreement of different approaches for?scalar?gauge-invariant metric perturbations during inflation

We revisit an extension of the well-known formalism for gauge-invariant scalar metric fluctuations to study the spectra for both the inflaton and gauge-invariant (scalar) metric fluctuations in the framework of a single-field inflationary model, in which the quasi-exponential expansion is driven by an inflaton which is minimally coupled to gravity. The proposal here examined is valid also for fluctuations with large amplitudes, but for cosmological scales, where vector and tensor perturbations can be neglected and the fluid is irrotacional.     

Quantum spin fluctuations in the spin-liquid state of Tb?Ti?O?

Neutron scattering experiments on a polycrystalline sample of the frustrated pyrochlore magnet Tb(2)Ti(2)O(7), which does not show any magnetic order down to 50 mK, have revealed that it shows condensation behavior below 0.4 K from a thermally fluctuating paramagnetic state to a spin-liquid ground state with quantum spin fluctuations. Energy spectra change from quasielastic scattering to a continuum with a double-peak structure at energies of 0 and 0.8 K in the spin-liquid state. Specific heat shows an anomaly at the crossover temperature.     

A class of chaotic bird calls?

Evidence is presented that the basic vocalized sound produced by some cockatoos, specifically the Australian sulfur-crested cockatoo (Cacatua galerita) and the gang-gang cockatoo (Callocephalon fimbriatum), has a chaotic acoustic structure rather than the harmonic structure characteristic of most birdsongs. These findings support those of Fee et al. [Nature (London) 395(3), 67-71 (1999)] on nonlinear period-doubling transitions in the song of the zebra finch (Taeniopygia guttata). It is suggested that syllables with chaotic structure may be a feature of the songs of many birds.     

Semisuperfluidity of 3He in aerogel?

According to hydrodynamic, acoustic, and NMR studies the superfluid transition temperature of 3He in aerogel ( T(a)(c)) is significantly suppressed with respect to that of bulk 3He. We have found in the range of temperatures between T(c) and T(a)(c) a large and unexpected NMR satellite line attributable to the liquid inside the aerogel. We propose that this anomalous behavior of liquid 3He corresponds to a new type of superfluid ordering related to magnetic and possibly orbital coherence.