International Journal of Modern Physics D

The braneworld description of our universe entails a large extra dimension and a fundamental scale of gravity that might be lower by several orders of magnitude compared to the Planck scale. An interesting consequence of the braneworld scenario is in the nature of spherically symmetric vacuum solutions to the brane gravitational field equations which could represent black holes with properties quite distinct compared to ordinary black holes in 4-dimensions. We discuss certain key features of some braneworld black hole geometries. Such black holes are likely to have diverse cosmological and astrophysical ramifications. The cosmological evolution of primordial braneworld black holes is described highlighting their longevity due to modified evaporation and effective accretion of radiation during the early braneworld high energy era. Observational abundance of various evaporation products of the black holes at different eras impose constraints on their initial mass fraction. Surviving primordial black holes could be candidates of dark matter present in galactic haloes. We discuss gravitational lensing by braneworld black holes. Observables related to the relativistic images of strong field gravitational lensing could in principle be used to distinguish between different braneworld black hole metrics in future observations.

We investigate refined algebraic quantization with group averaging in a constrained Hamiltonian system whose gauge group is the connected component of the lower triangular subgroup of SL(2, ℝ). The unreduced phase space is T*ℝ^p+q with p≥1 and q≥1, and the system has a distinguished classical observable algebra. Group averaging with the geometric average of the right and left invariant measures, invariant under the group inverse, yields a Hilbert space that carries a maximally degenerate principal unitary series representation of O(p, q). The representation is nontrivial iff (p, q) ≠ (1, 1), which is also the condition for the classical reduced phase space to be a symplectic manifold up to a singular subset of measure zero. We present a detailed comparison to an algebraic quantization that imposes the constraints in the sense Ĥ_a Ψ = 0 and postulates self-adjointness of the observables. Under certain technical assumptions that parallel those of the group averaging theory, this algebraic quantization gives no quantum theory when (p, q) = (1, 2) or (2, 1), or when p≥2, q≥2 and p+q ≡1 (mod 2).

We present a critical analysis concerning the electromagnetic waves propagation on a curved space–time and the correct applicability of the equivalence principle to this phenomenon. In particular we discuss this phenomenon with respect to the Universe background, by showing how any physical wavelength (indeed only those much less than the radius of curvature) could, in principle, freely propagate arbitrarily close to the initial Big-Bang. It is followed by a discussion on the real meaning of the horizons paradox solution, based on extending the result of the classical analysis to the wavelengths of photons present in the primordial thermal bath.

The new results of spectrophotometry, and X-ray imaging spectroscopy observations for the high-polarization, radio-loud and Gev gamma-ray-loud blazar PKS 1510-089 have been observed. The main results show that: (1) A double-horned broad H_β line in the spectrum of PKS 1510-089 has been discovered. The H_β double-peaked emission profiles are impressive with the line asymmetry that the red peak seems to be higher than the blue peak; (2) The observation of X-rays, performed with the ACIS-S detector aboard the Chandra X-ray observatory, led to the discovery of a bending X-ray jet, coincident with the radio arcsecond jet of PKS 1510-089; (3) According to the reverberation mapping method and the empirical relation between the broad line region (BLR) size and the optical continuum luminosity at 5100 Å (the rest frame), we obtained the Virial mass of the central primary black hole, which coincides with our previous result by extremely rapid optical variability method. In addition, based on these new observational results mentioned above and the other previous observations, we have discussed the theoretical models for PKS 1510-089.

X-ray spectral parameters were determined for WZ Sge observed with the ROSAT PSPC. The raw data were fitted with various spectral models and the best fit spectral models are found to be that of Raymond–Smith and Thermal Bremsstrahlung. The best fit temperature was estimated to be kT ~ 2.17 keV while the column density was found to be N_H ~ 2.8 × 10²⁰cm^-2. The estimated 0.1–2.4 keV flux was in the range of log F = -12 ergs cm^-2s^-1.

WZ Sge stars show long outburst recurrence times and weak X-ray emissions during the quiescence states. It is possible to lengthen repetition cycles by decreasing the viscosity parameter (α); however there still remains the question why α is so small, specifically for these objects. The Coronal Siphon Model of Meyer and Meyer–Hofmeister¹ can explain these phenomenons successfully. For this reason, the equations of this model were applied to the results of spectral analysis. Using this model, the mass accretion rate, mass evaporation rate in corona and the radius of the corona were calculated to be 10^14.48 gr yr^-1, 10^-5.4 gr cm^-2 s^-1 and 10^9.7 cm, respectively. The obtained values suggest that the corona model can indeed operate in WZ Sge system.

We present a geometrical unification theory in a Kaluza–Klein approach that achieve the geometrization of a generic gauge theory bosonic component.

We show how it is possible to derive gauge charge conservation from the invariance of the model under extra-dimensional translations and to geometrize gauge connections for spinors, in order to make possible to introducing matter just through free spinorial fields. Then we present the applications to (i) a pentadimensional manifold V⁴ ⊗ S¹ so reproducing the original Kaluza–Klein theory with some extensions related to the rule of the scalar field contained in the metric and to the introduction of matter through spinors with a phase dependance from the fifth coordinate, (ii) a seven-dimensional manifold V⁴ ⊗ S¹ ⊗ S², in which we geometrize the electroweak model by introducing two spinors for every leptonic family and quark generation and a scalar field with two components with opposite hypercharge responsible for spontaneous symmetry breaking.

We seek an analogy of the mathematical form of the alternative form of Einstein's field equations for Lovelock's field equations. We find that the price for this analogy is to accept the existence of the trace anomaly of the energy–momentum tensor even in classical treatments. As an example, we take this analogy to any generic second order Lagrangian and exactly derive the trace anomaly relation suggested by Duff. This indicates that an intrinsic reason for the existence of such a relation should perhaps be, classically, somehow related to the covariance of the form of Einstein's equations.

The manifestation of point sources in the upcoming Planck maps is a direct reflection of the properties of the pixelized antenna beam shape for each frequency, which is related to the scan strategy, pointing accuracy, noise properties and map-making algorithm. In this paper we firstly compare analytically two filters for the Planck point source extraction, namely, the adaptive top-hat filter (ATHF) and the theoretically-optimal filter (TOF). Our analyses are based on the premise that the required experiment parameters of the TOF are assumed to be already known: the CMB and noise power spectrum and a circular Gaussian beam shape and size. Whereas, the ATHF does not need any a priori knowledge. The analyses show that the TOF is optimal in terms of the gain after the parameter inputs. We simulate the Planck HFI 100 GHz channel with elliptical beam in rotation to test the efficiency of the TOF and the ATHF. We also apply the ATHF on the WMAP Q-band map and the derived map (the foreground-cleaned map by Tegmark, de Oliveira Costa & Hamilton) from the WMAP one-year data. The uncertainties on the angular power spectrum will hamper the efficiency of the TOF. The ATHF is computationally efficient in tackling more realistic data such as the following effects: an elliptical beam with slow precession and the change of the beam ellipticity ratio due to possible mirror degradation. The ATHF is well suited for the construction of the Planck Early Release Compact Source Catalogue.

We present a detailed analysis on the phases of the WMAP foregrounds (synchrotron, free–free and dust emission) of the WMAP K–W bands in order to estimate the significance of the variation of the spectral indices at different components. We first extract the spectral-index varying signals by assuming that the invariant part among different frequency bands have 100% cross-correlation of phases. We then use the minimization of variance, which is normally used for extracting the CMB signals, to extract the frequency independent signals. Such a common signal in each foreground component could play a significant role for any kind of component separation methods, because the methods cannot discriminate frequency independent foregrounds and CMB.