Andrei Gruzinov

Solar fusion cross-sections

We review and analyze the available information on the nuclear-fusion cross sections that are most important for solar energy generation and solar neutrino production. We provide best values for the low-energy cross-section factors and, wherever possible, estimates of the uncertainties. We also describe the most important experiments and calculations that are required in order to improve our knowledge of solar fusion rates.

Fuzzy cold dark matter: the wave properties of ultralight particles.

There is an asymmetry between the mass of the electric charges, for example proton and electron, can understood by the asymmetrical Planck Distribution Law. This temperature dependent energy distribution is asymmetric around the maximum intensity, where the annihilation of matter and antimatter is a high probability event. The asymmetric sides are creating different frequencies of electromagnetic radiations being in the same intensity level and compensating each other. One of these compensating ratios is the electron – proton mass ratio. The lower energy side has no compensating intensity level, it is the dark energy and the corresponding matter is the dark matter.

CONVECTION-DOMINATED ACCRETION FLOWS

Nonradiating advection-dominated accretion flows are convectively unstable in the radial direction. We calculate the two-dimensional (r-θ) structure of such flows assuming that (1) convection transports angular momentum inward, opposite to normal viscosity, and (2) viscous transport by other mechanisms (e.g., magnetic fields) is weak (α 1). Under such conditions convection dominates the dynamics of the accretion flow and leads to a steady state structure that is marginally stable to convection. We show that the marginally stable flow has a constant temperature and rotational velocity on spherical shells, a net flux of energy from small to large radii, zero net accretion rate, and a radial density profile of ρ ∝ r-1/2, flatter than the ρ ∝ r-3/2 profile characteristic of spherical accretion flows. This solution accurately describes the full two-dimensional structure of recent axisymmetric numerical simulations of advection-dominated accretion flows.

TURBULENCE AND PARTICLE HEATING IN ADVECTION-DOMINATED ACCRETION FLOWS

We extend and reconcile recent work on turbulence and particle heating in advection-dominated acc- retion —ows. For approximately equipartition magnetic —elds, the turbulence primarily heats the elec- trons. For weaker magnetic —elds, the protons are primarily heated. The division between electron and proton heating occurs between b D 5 and b D 100 (b is the ratio of gas to magnetic pressure), depending on unknown details of how waves are converted into whistlers on scales of the proton Larmor Alfvec n radius. We also discuss the possibility that magnetic reconnection could be a signi—cant source of elec- tron heating. Subject headings: accretion, accretion disksMHDplasmasturbulence

Secondary cosmic microwave background anisotropies in a universe reionized in patches

In a universe reionized in patches, the Doppler effect from Thomson scattering off free electrons generates secondary cosmic microwave background (CMB) anisotropies. For a simple model with small patches and late reionization, we analytically calculate the anisotropy power spectrum. Patchy reionization can, in principle, be the main source of anisotropies on arcminute scales. On larger angular scales, its contribution to the CMB power spectrum is a small fraction of the primary signal and is only barely detectable in the power spectrum with even an ideal, i.e., cosmic variance limited, experiment and an extreme model of reionization. Consequently, patchy reionization is unlikely to affect cosmological parameter estimation from the acoustic peaks in the CMB. Its detection on small angles would help determine the ionization history of the universe, in particular, the typical size of the ionized region and the duration of the reionization process.

Constraining the Accretion Rate onto Sagittarius A* Using Linear Polarization

Two possible explanations for the low luminosity of the supermassive black hole at the center of our Galaxy are (1) an accretion rate of the order of the canonical Bondi value (~10-5 M? yr-1) but a very low radiative efficiency for the accreting gas or (2) an accretion rate much less than the Bondi rate. Both models can explain the broadband spectrum of the Galactic center. We show that they can be distinguished using the linear polarization of synchrotron radiation. Accretion at the Bondi rate predicts no linear polarization at any frequency because of Faraday depolarization. Low accretion rate models, on the other hand, have much lower gas densities and magnetic field strengths close to the black hole; polarization may therefore be observable at high frequencies. If confirmed, a recent detection of linear polarization from Sgr A* at 150 GHz argues for an accretion rate of ~10-8 M? yr-1, much less than the Bondi rate. This test can be applied to other low-luminosity galactic nuclei.

Power of an Axisymmetric Pulsar

Certain exact properties of the stationary force-free magnetosphere of an axisymmetric pulsar are obtained. In particular, it is shown that a magnetic separatrix has an inclination angle of 77.3 degrees to the equatorial plane. The electromagnetic field has an R(-1/2) singularity inside the separatrix near the light cylinder. A numerical simulation of the magnetosphere which crudely reproduces these properties is presented. The numerical results are used to estimate the power of an axisymmetric pulsar: L=(1+/-0.1)mu(2)Omega(4)/c(3). Thus, the background magnetic configuration, on which all the puzzling pulsar phenomena are taking place, is now known with some confidence.

Screening in Thermonuclear Reaction Rates in the Sun

We evaluate the effect of electrostatic screening by ions and electrons on low-Z thermonuclear reactions in the Sun. We use a mean field formalism and calculate the electron density of the screening cloud using the appropriate density matrix equation of quantum statistical mechanics. Because of well-understood physical effects that are included for the first time in our treatment, the calculated enhancement of reaction rates does not agree with the frequently used interpolation formulae. Our result does agree, within small uncertainties, with Salpeters weak screening formula. If weak screening is used instead of the commonly employed screening prescription of Graboske et al., the predicted 8B neutrino flux is increased by 7% and the predicted chlorine rate is increased by 0.4 SNU.

Radiative efficiency of collisionless accretion

The radiative efficiency, η ≡ L/c2, of a slowly accreting black hole is estimated using a two-temperature model of accretion. The radiative efficiency depends on the magnetic field strength near the Schwarzschild radius. For weak magnetic fields, i.e., β-1 ≡ B2/8πp 10-3, the low efficiency η ~ 10-4 that is assumed in some theoretical models is achieved. For β-1 > 10-3, a significant fraction of viscous heat is dissipated by electrons and radiated away resulting in η > 10-4. At equipartition magnetic fields, β-1 ~ 1, we estimate η ~ 10-1.

Strongly Polarized Optical Afterglows of Gamma-Ray Bursts

The optical afterglows of the gamma-ray bursts can be strongly polarized, in principle up to tens of percents, if (1) the afterglow is synchrotron radiation from an ultrarelativistic blast, (2) the blast is beamed during the afterglow phase, i.e., the shock propagates within a narrow jet, (3) we observe at the right time from the right viewing angle, and (4) magnetic fields parallel and perpendicular to the jet have different proper strengths.