Continuous matter creation and the acceleration of the universe: the growth of density fluctuations

Cosmologies including continuous matter creation are able to reproduce the main properties of the standard $\Lambda$CDM model, in particular in cases where the particle and entropy production rates are equal. These specific models, characterized by a mass density equal to the critical value, behave like the standard $\Lambda$CDM model at early times whereas their late evolution is similar to the steady-state cosmology. The maximum amplitude of density fluctuations in these models depends on the adopted creation rate, related here to the parameter $\Omega_v$ and this limitation could be a difficulty for the formation of galaxies and large-scale structure in this class of universe. Additional problems are related with predictions either of the random peculiar velocities of galaxies or the present density of massive clusters of galaxies, both being largely overestimated with respect to observational data.Comment: 11 pages, 2 figures, accepted for publication in General Relativity and Gravitatio

Gravitation Wave Emission from Radio Pulsars Revisited

We report a new pulsar population synthesis based on Monte Carlo techniques, aiming to estimate the contribution of galactic radio pulsars to the continuous gravitational wave emission. Assuming that the rotation periods of pulsars at birth have a Gaussian distribution, we find that the average initial period is 290 ms. The number of objects with periods equal to or less than 0.4 s, and therefore capable of being detected by an interferometric gravitational antenna like VIRGO, is of the order of 5100-7800. With integration times lasting between 2 and 3 yr, our simulations suggest that about two detections should be possible, if the mean equatorial ellipticity of the pulsars is $\epsilon$ =10$^{-6}$. A mean ellipticity an order of magnitude higher increases the expected number of detections to 12-18, whereas for $\epsilon < 10^{-6}$, no detections are expectedComment: accepted for publication in A&A, 9 pages, 8 figure

Subleading Logarithmic QED Initial State Corrections to e+e−→γ∗/Z0∗e^+e^- \rightarrow \gamma^*/{Z^{0}}^* to O(α6L5)O(\alpha^6 L^5)

Using the method of massive operator matrix elements, we calculate the subleading QED initial state radiative corrections to the process $e^+e^- \rightarrow \gamma^*/Z^*$ for the first three logarithmic contributions from $O(\alpha^3 L^3), O(\alpha^3 L^2), O(\alpha^3 L)$ to $O(\alpha^5 L^5), O(\alpha^5 L^4), O(\alpha^5 L^3)$ and compare their effects to the leading contribution $O(\alpha^6 L^6)$ and one more subleading term $O(\alpha^6 L^5)$. The calculation is performed in the limit of large center of mass energies squared $s \gg m_e^2$. These terms supplement the known corrections to $O(\alpha^2)$, which were completed recently. Given the high precision at future colliders operating at very large luminosity, these corrections are important for concise theoretical predictions. The present calculation needs the calculation of one more two--loop massive operator matrix element in QED. The radiators are obtained as solutions of the associated Callen--Symanzik equations in the massive case. The radiators can be expressed in terms of harmonic polylogarithms to weight {\sf w = 6} of argument $z$ and $(1-z)$ and in Mellin $N$ space by generalized harmonic sums. Numerical results are presented on the position of the $Z$ peak and corrections to the $Z$ width, $\Gamma_Z$. The corrections calculated result into a final theoretical accuracy for $\delta M_Z$ and $\delta \Gamma_Z$ which is estimated to be of O(30 keV) at an anticipated systematic accuracy at the FCC\_ee of \sim 100 keV. This precision cannot be reached, however, by including only the corrections up to $O(\alpha^3)$.Comment: 58 pages, 3 Figure

Ages of Elliptical Galaxies: Single versus Multi Population Interpretation

New calibrations of spectrophotometric indices of elliptical galaxies as functions of spectrophotometric indices are presented, permitting estimates of mean stellar population ages and metallicities. These calibrations are based on evolutionary models including a two-phase interstellar medium, infall and a galactic wind.Free parameters were fixed by requiring that models reproduce the mean trend of data in the color-magnitude diagram as well as in the plane of indices Hbeta-Mg2 and Mg2-. To improve the location of faint ellipticals(MB > -20) in the Hbeta-Mg2 diagram, down-sizing was introduced. An application of our calibrations to a sample of ellipticals and a comparison with results derived from single stellar population models is given. Our models indicate that mean population ages span an interval of 7-12 Gyr and are correlated with metallicities, which range from approximately half up to three times solar.Comment: 10 pages and 6 figures. Accepted for publication in Monthly Notices of the Royal Astronomical Society Main Journa

Forfeiture of Attorney\u27s Fees Under RICO and CCE

We present the matching relations of the variable flavor number scheme at next-to-leading order, which are of importance to define heavy quark partonic distributions for the use at high energy colliders such as Tevatron and the LHC. The consideration of the two-mass effects due to both charm and bottom quarks, having rather similar masses, are important. These effects have not been considered in previous investigations. Numerical results are presented for a wide range of scales. We also present the corresponding contributions to the structure function $F_2(x,Q^2)$

The Three Loop Two-Mass Contribution to the Gluon Vacuum Polarization

We calculate the two-mass contribution to the 3-loop vacuum polarization of the gluon in Quantum Chromodynamics at virtuality $p^2 = 0$ for general masses and also present the analogous result for the photon in Quantum Electrodynamics.Comment: 5 pages Late