Inflation in Bianchi models and the cosmic no hair theorem in brane world

In this paper, the cosmic no hair theorem for anisotropic Bianchi models which admit inflation with a scalar field is studied in the framework of Brane world. It is found that all Bianchi models except Bianchi type IX, transit to an inflationary regime with vanishing anisotropy. In the Brane world, anisotropic universe approaches the inflationary era much faster than that in the general theory of relativity. The form of the potential does not affect the evolution in the inflationary epoch. However, the late time behaviour is controlled by a constant additive factor in the potential for the inflaton field.Comment: 12 pages, no figures, submitted to Phys. Rev.

Is 4U 0114+65 an eclipsing HMXB?

We present the pulsation and spectral characteristics of the HMXB 4U 0114+65 during a \emph{Suzaku} observation covering the part of the orbit that included the previously known low intensity emission of the source (dip) and the egress from this state. This dip has been interpreted in previous works as an X-ray eclipse. Notably, in this Suzaku observation, the count rate during and outside the dip vary by a factor of only 2-4 at odds with the eclipses of other HMXBs, where the intensity drops upto two orders of magnitude. The orbital intensity profile of 4U 0114+65 is characterized by a narrow dip in the RXTE-ASM (2-12 \rm{keV}) light curve and a shallower one in the Swift-BAT (15-50 \rm{keV}), which is different from eclipse ingress/egress behaviour of other HMXBs. The time-resolved spectral analysis reveal moderate absorption column density (N$_{H}$ - 2-20 $\times$ $10^{22}$ atoms $cm^{-2}$) and a relatively low equivalent width ($\sim$ 30 \rm{eV} \& 12 \rm{eV} of the iron K$_\alpha$ and K$_\beta$ lines respectively) as opposed to the typical X-ray spectra of HMXBs during eclipse where the equivalent width is $\sim$ 1 \rm{keV}. Both XIS and PIN data show clear pulsations during the dip, which we have further confirmed using the entire archival data of the IBIS/ISGRI and JEM-X instruments onboard \emph{INTEGRAL}. The results we presented question the previous interpretation of the dip in the light curve of 4U 0114+65 as an X-ray eclipse. We thus discuss alternative interpretations of the periodic dip in the light curve of 4U 0114+65.Comment: 16 pages, 7 figures, 1 table, Accepted in MNRA

Variations of the harmonic components of the X-ray Pulse Profile of PSR B1509-58

We used the Fourier decomposition technique to investigate the stability of the X-ray pulse profile of a young pulsar PSR B1509-58 by studying the relative amplitudes and the phase differences of its harmonic components with respect to the fundamental using data from the Rossi X-Ray Timing Explorer. Like most young rotation powered pulsars, PSR B1509-58 has a high spin down rate. It also has less timing noise allowing accurate measurement of higher order frequency derivatives which in turn helps in study of the physics of pulsar spin down. Detailed investigation of pulse profiles over the years will help us establish any possible connection between the timing characteristics and the high energy emission characteristics for this pulsar. Further, the study of pulse profiles of short period X-ray pulsars can also be useful for using them as means of interplanetary navigation system. The X-ray pulse profile of this source has been analysed for 15 $\rm years$ (1996-2011). The long term average amplitudes of the first, second and third harmonics (and their standard deviation for individual measurements) compared to the fundamental are 36.9 % (1.7 %), 13.4 % (1.9 %) and 9.4 % (1.8 %) respectively. Similarly, the phases of the three harmonics (and standard deviations) with respect to the fundamental are 0.36 (0.06), 1.5 (0.2), 2.5 (0.3) $\rm radian$ respectively. We do not find any significant variation of the harmonic components of the pulse profile in comparison to the fundamental.Comment: 10 pages, 7 figure

Interacting Holographic Generalized Chaplygin Gas in compact Kaluza-Klein cosmology

We investigate Holographic Dark Energy Correspondence of Interacting Generalized Chaplygin Gas model in the framework of compact Kaluza-Klein cosmology. The evolution of the modified holographic dark energy and the equation of state parameter is obtained here.Using the present observational value of density parameter a stable configuration is formed which accommodates Dark Energy. we note a connection between Dark Energy and Phantom field and have shown that Dark Energy might have evolved from a Phantom state in the past.Comment: 4 pages, 2 figures, pdftex, communicated to Euro. Phys. Let

Observational Constraints on the Model Parameters of a Class of Emergent Universe

A class of Emergent Universe (EU) model is studied in the light of recent observational data. Significant constraints on model parameters are obtained from the observational data. Density parameter for a class of model is evaluated. Some of the models are in favour of the recent observations. Some models have been found which are not interesting yielding unrealistic present day value of the density parameter.Comment: Uses mn2e class file, 5 pages, 9 figures. (submitted to MNRAS