We reconsider the virial theorem in the presence of a positive cosmological constant Λ. Assuming steady state, we derive an inequality of the form ρ ≥ A(Λ/4πGN ) for the mean density ρ of the astrophysical object. The parameter A depends only on the shape of the object. With a minimum at Asphere = 2, its value can increase by several orders of magnitude as the shape of the object deviates from ...

This paper investigates the global chaos synchronization of identical hyperchaotic Newton-Leipnik systems (Ghosh and Bhattacharya, 2010) by sliding mode control. The stability results derived in this paper for the complete synchronization of identical hyperchaotic Newton-Leipnik chaotic systems are established using Lyapunov stability theory. Since the Lyapunov exponents are not required for th...

The dynamical effect of the cosmological constant Λ on a single spherical void evolving in a the universe is investigated within a non linear perturbation of Newton-Friedmann models. The void expands with a huge initial burst which freezes asymptotically with time up to matching Hubble flow. For Ω◦ ∼ 0.3, Λ-effect on the kinematics intervenes significantly by amplifying the expansion rate at re...

We report on a timing analysis performed on a 62-ks long XMM-Newton observation of the accreting millisecond pulsar SAX J1808.4–3658 during the latest X-ray outburst which started on September 21st 2008. By connecting the time of arrivals of the pulses observed during the XMM-Newton observation we derived the best fit orbital solution and a best fit value of the spin period for the 2008 outburs...

In this paper, we solve Riccati equations by using the fractional-order hybrid function of block-pulse functions and Bernoulli polynomials (FOHBPB), obtained replacing x with xα, positive α. Fractional derivatives are in Caputo sense. With help incomplete beta functions, able to build exactly Riemann–Liouville fractional integral operator associated FOHBPB. This operator, together Newton–Cotes ...

In April 2001 SN1993J was observed with both the PN and MOS cameras of the XMM-Newton observatory, resulting in about 7 × 10 4 s of acceptable observation time. Fit results with both the PN and MOS2 camera spectra studying different spectral models are presented. The spectra are best fitted in the energy range between 0.3 and ∼ 10 keV by a 2-component thermal model with temperatures of kT1 = 0....

In [Cha00] Chai made a conjecture on the codimensions of Newton strata in Shimura varieties, which then led Rapoport [Rap05] to his conjecture on dimensions of affine Deligne-Lusztig varieties inside affine Grassmannians. The main goal of this paper is to show that exactly the same codimensions arise in a simpler context, that of the Newton stratification in the adjoint quotient of a reductive ...

We have conducted a survey of X-ray sources in XMM-Newton observations of M31, examining their power density spectra (PDS) and spectral energy distributions (SEDs). Our automated source detection yielded 535 good X-ray sources; to date, we have studied 225 of them. In particular, we examined the PDS because low mass X-ray binaries (LMXBs) exhibit two distinctive types of PDS. At low accretion r...

This article focuses on the process of approximating a definite integral from values of the integrand when exact mathematical integration is not available. This problem arises in statistics when marginal density functions or expected values of random variables are required. The article describes classical univariate quadrature methods including the trapezoidal rule, Simpson’s rule, Newton-Cotes...