The Future Evolution of White Dwarf Stars Through Baryon Decay and Time Varying Gravitational Constant

Motivated by the possibility that the fundamental ``constants'' of nature could vary with time, this paper considers the long term evolution of white dwarf stars under the combined action of proton decay and variations in the gravitational constant. White dwarfs are thus used as a theoretical laboratory to study the effects of possible time variations, especially their implications for the future history of the universe. More specifically, we consider the gravitational constant $G$ to vary according to the parametric relation $G = G_0 (1 + t/t_\ast)^{-p}$, where the time scale $t_\ast$ is the same order as the proton lifetime. We then study the long term fate and evolution of white dwarf stars. This treatment begins when proton decay dominates the stellar luminosity, and ends when the star becomes optically thin to its internal radiation.Comment: 12 pages, 10 figures, accepted to Astrophysics and Space Scienc

Chiral rings and GSO projection in Orbifolds

The GSO projection in the twisted sector of orbifold background is sometimes subtle and incompatible descriptions are found in literatures. Here, from the equivalence of partition functions in NSR and GS formalisms, we give a simple rule of GSO projection for the chiral rings of string theory in \C^r/\Z_n, $r=1,2,3$. Necessary constructions of chiral rings are given by explicit mode analysis.Comment: 24 page

Large deviations for many Brownian bridges with symmetrised initial-terminal condition

Consider a large system of $N$ Brownian motions in $\mathbb{R}^d$ with some non-degenerate initial measure on some fixed time interval $[0,\beta]$ with symmetrised initial-terminal condition. That is, for any $i$, the terminal location of the $i$-th motion is affixed to the initial point of the $\sigma(i)$-th motion, where $\sigma$ is a uniformly distributed random permutation of $1,...,N$. Such systems play an important role in quantum physics in the description of Boson systems at positive temperature $1/\beta$. In this paper, we describe the large-N behaviour of the empirical path measure (the mean of the Dirac measures in the $N$ paths) and of the mean of the normalised occupation measures of the $N$ motions in terms of large deviations principles. The rate functions are given as variational formulas involving certain entropies and Fenchel-Legendre transforms. Consequences are drawn for asymptotic independence statements and laws of large numbers. In the special case related to quantum physics, our rate function for the occupation measures turns out to be equal to the well-known Donsker-Varadhan rate function for the occupation measures of one motion in the limit of diverging time. This enables us to prove a simple formula for the large-N asymptotic of the symmetrised trace of ${\rm e}^{-\beta \mathcal{H}_N}$, where $\mathcal{H}_N$ is an $N$-particle Hamilton operator in a trap

Transition Radiation by Neutrinos

We calculate the transition radiation process $\nu \to \nu \gamma$ at an interface of two media. The neutrinos are taken to be with only standard-model couplings. The medium fulfills the dual purpose of inducing an effective neutrino-photon vertex and of modifying the photon dispersion relation. The transition radiation occurs when at least one of those quantities have different values in different media. The neutrino mass is ignored due to its negligible contribution. We present a result for the probability of the transition radiation which is both accurate and analytic. For $E_\nu =1$ MeV neutrino crossing polyethylene-vacuum interface the transition radiation probability is about $10^{-39}$ and the energy intensity is about $10^{-34}$ eV. At the surface of the neutron stars the transition radiation probability may be $\sim 10^{-20}$. Our result on three orders of magnitude is larger than the results of previous calculations

Mpox Virus in Pregnancy, the Placenta, and Newborn.

Before its eradication, the smallpox virus was a significant cause of poor obstetric outcomes, including maternal and fetal morbidity and mortality. The mpox (monkeypox) virus is now the most pathogenic member of the Orthopoxvirus genus infecting humans. The 2022 global mpox outbreak has focused attention on its potential effects during pregnancy. To understand the comparative effects of different poxvirus infections on pregnancy, including mpox virus, variola virus, vaccinia virus, and cowpox virus. The impact on the pregnant individual, fetus, and placenta will be examined, with particular attention to the occurrence of intrauterine vertical transmission and congenital infection. The data are obtained from the authors' cases and from various published sources, including early historical information and contemporary publications. Smallpox caused maternal and perinatal death, with numerous cases reported of intrauterine transmission. In endemic African countries, mpox has also affected pregnant individuals, with up to a 75% perinatal case fatality rate. Since the start of the 2022 mpox outbreak, increasing numbers of pregnant women have been infected with the virus. A detailed description is given of the congenital mpox syndrome in a stillborn fetus, resulting from maternal-fetal transmission and placental infection, and the potential mechanisms of intrauterine infection are discussed. Other poxviruses, notably vaccinia virus and, in 1 case, cowpox virus, can also cause perinatal infection. Based on the historical evidence of poxvirus infections, mpox remains a threat to the pregnant population, and it can be expected that additional cases will occur in the future

Topological and topological-electronic correlations in amorphous silicon

In this paper, we study several structural models of amorphous silicon, and discuss structural and electronic features common to all. We note spatial correlations between short bonds, and similar correlations between long bonds. Such effects persist under a first principles relaxation of the system and at finite temperature. Next we explore the nature of the band tail states and find the states to possess a filamentary structure. We detail correlations between local geometry and the band tails.Comment: 7 pages, 11 figures, submitted to Journal of Crystalline Solid

Eccentricities of Planets in Binary Systems

The most puzzling property of the extrasolar planets discovered by recent radial velocity surveys is their high orbital eccentricities, which are very difficult to explain within our current theoretical paradigm for planet formation. Current data reveal that at least 25% of these planets, including some with particularly high eccentricities, are orbiting a component of a binary star system. The presence of a distant companion can cause significant secular perturbations in the orbit of a planet. At high relative inclinations, large-amplitude, periodic eccentricity perturbations can occur. These are known as "Kozai cycles" and their amplitude is purely dependent on the relative orbital inclination. Assuming that every planet host star also has a (possibly unseen, e.g., substellar) distant companion, with reasonable distributions of orbital parameters and masses, we determine the resulting eccentricity distribution of planets and compare it to observations? We find that perturbations from a binary companion always appear to produce an excess of planets with both very high (e>0.6) and very low (e<0.1) eccentricities. The paucity of near-circular orbits in the observed sample implies that at least one additional mechanism must be increasing eccentricities. On the other hand, the overproduction of very high eccentricities observed in our models could be combined with plausible circularization mechanisms (e.g., friction from residual gas) to create more planets with intermediate eccentricities (e=0.1-0.6).Comment: 8 pages, to appear in "Close Binaries in the 21st Century: New Opportunities and Challenges", ed. A. Gimenez et al. (Springer

Effects of Temperature and Moisture on Sheet Molding Compounds

A summary is given on the effects of moisture and temperature on the properties of chopped fiber reinforced sheet molding compounds. The properties surveyed include tensile strength and modulus, compression strength and modulus, shear strength and modulus, flexural strength and modulus, fatigue, creep, vibration damping, moisture absorption characteristics, and thermal expansion.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68648/2/10.1177_073168448300200201.pd