The effects of an extra U(1) axial condensate on the radiative decay eta' --> gamma gamma at finite temperature

Supported by recent lattice results, we consider a scenario in which a U(1)-breaking condensate survives across the chiral transition in QCD. This scenario has important consequences on the pseudoscalar-meson sector, which can be studied using an effective Lagrangian model. In particular, generalizing the results obtained in a previous paper (where the zero-temperature case was considered), we study the effects of this U(1) chiral condensate on the radiative decay eta' --> gamma gamma at finite temperature.Comment: 15 pages, LaTeX fil

Generalized Effective Reducibility

We introduce two notions of effective reducibility for set-theoretical statements, based on computability with Ordinal Turing Machines (OTMs), one of which resembles Turing reducibility while the other is modelled after Weihrauch reducibility. We give sample applications by showing that certain (algebraic) constructions are not effective in the OTM-sense and considerung the effective equivalence of various versions of the axiom of choice

The spectroscopic evolution of the symbiotic star AG Draconis. I.The O VI Raman, Balmer, and helium emission line variations during the outburst of 2006-2008

AG Dra is one of a small group of low metallicity S-type symbiotic binaries with K-type giants that undergoes occasional short-term outbursts of unknown origin. Our aim is to study the behavior of the white dwarf during an outburst using the optical Raman lines and other emission features in the red giant wind. The goal is to determine changes in the envelope and the wind of the gainer in this system during a major outburst event and to study the coupling between the UV and optical during a major outburst. Using medium and high resolution groundbased optical spectra and comparisons with archival $FUSE$ and $HST/STIS$ spectra, we study the evolution of the Raman O VI features and the Balmer, He I, and He II lines during the outburst from 2006 Sept. through 2007 May and include more recent observations (2009) to study the subsequent evolution of the source. The O VI Raman features disappeared completely at the peak of the major outburst and the subsequent variation differs substantially from that reported during the previous decade. The He I and He II lines, and the Balmer lines, vary in phase with the Raman features but there is a double-valuedness to the He I 6678, 7065 relative to the O VI Raman 6825\AA\ variations in the period between 2006-2008 that has not been previously reported. The variations in the Raman feature ratio through the outburst interval are consistent with the disappearance of the O VI FUV resonance wind lines from the white dwarf and of the surrounding O$^{+5}$ ionized region within the red giant wind provoked by the expansion and cooling of the white dwarf photosphere.Comment: 10 pages, 15 figs. A&A (in press, accepted for publication 23/11/2009

Multi-wavelength spectroscopic study of shock-driven phenomena in explosive outbursts in symbiotic-like recurrent novae with an emphasis on RS Ophiuchi

Aims. Our goal is to detail the development of RS Ophiuchi and the other Galactic symbiotic-like recurrent novae throughout their outburst and quiescence, with a particular emphasis on the propagation of the shock wave during the outburst of the binaries. Methods. The spectral analysis has been performed using archival data according to the features of the individual datasets. Swift grism spectra were reduced and extracted using a combination of the pre-existing UVOTPY Python routine and newly written pipelines in Matlab. Other datasets were directly available in reduced form, already corrected for instrumental or background contamination, and calibrated in wavelength and flux or intensity. The work on these was done through pipelines suited for reading the data and elaborating them to extract quantities of interest for the analysis. Results. We find striking similarities in different outbursts of the same object and for different novae. For example, RS Oph 2021 was almost identical to the 2006 outburst, despite having occurred at a different orbital phase with the observations made from a different line of sight through the red giant wind. Despite the intrinsically different properties of the binaries, striking similarities are found for different systems of the same class, for instance, the trend of the electron density over time during outburst appears to follow a general temporal development

The spectroscopic evolution of the symbiotic-like recurrent nova V407 Cygni during its 2010 outburst. I. The shock and its evolution

On 2010 Mar 10, V407 Cyg was discovered in outburst, eventually reaching V< 8 and detected by Fermi. Using medium and high resolution ground-based optical spectra, visual and Swift UV photometry, and Swift X-ray spectrophotometry, we describe the behavior of the high-velocity profile evolution for this nova during its first three months. The peak of the X-ray emission occurred at about day 40 with a broad maximum and decline after day 50. The main changes in the optical spectrum began at around that time. The He II 4686A line first appeared between days 7 and 14 and initially displayed a broad, symmetric profile that is characteristic of all species before day 60. Low-excitation lines remained comparatively narrow, with v(rad,max) of order 200-400 km/s. They were systematically more symmetric than lines such as [Ca V], [Fe VII], [Fe X], and He II, all of which showed a sequence of profile changes going from symmetric to a blue wing similar to that of the low ionization species but with a red wing extended to as high as 600 km/s . The Na I D doublet developed a broad component with similar velocity width to the other low-ionization species. The O VI Raman features were not detected. We interpret these variations as aspherical expansion of the ejecta within the Mira wind. The blue side is from the shock penetrating into the wind while the red wing is from the low-density periphery. The maximum radial velocities obey power laws, v(rad,max) t^{-n} with n ~ 1/3 for red wing and ~0.8 for the blue. (truncated)Comment: Accepted for publication, A&A (submitted: 9 Oct 2010; accepted: 1 Dec 2010) in press; based on data obtained with Swift, Nordic Optical Telescope, Ondrejov Observatory. Corrected typo, Fermi?LAT detection was at energies above 100 MeV (with thanks to C. C. Cheung

Transition Properties of Low Lying States in Atomic Indium

We present here the results of our relativistic many-body calculations of various properties of the first six low-lying excited states of indium. The calculations were performed using the relativistic coupled-cluster method in the framework of the singles, doubles and partial triples approximation. We obtain a large lifetime ~10s for the [4p^6]5s^2 5p_{3/2} state, which had not been known earlier. Our precise results could be used to shed light on the reliability of the lifetime measurements of the excited states of atomic indium that we have considered in the present work.Comment: 6 pages, 1 figure and 3 table

Galaxy Formation by Galactic Magnetic Fields

Galaxies exhibit a sequence of various morphological types, i.e., the Hubble sequence, and they are basically composed of spheroidal components (elliptical galaxies and bulges in spiral galaxies) and disks. It is known that spheroidal components are found only in relatively massive galaxies with M=10^{10-12} M_sun, and all stellar populations in them are very old, but there is no clear explanation for these facts. Here we present a speculative scenario for the origin of the Hubble sequence, in which magnetic fields ubiquitously seen in galaxies have played a crucial role. We first start from a strange observational fact that magnetic field strengths observed in spiral galaxies sharply concentrate at a few microgauss, for a wide range of galaxy luminosity and types. We then argue that this fact and the observed correlation between star formation activity and magnetic field strength in spiral galaxies suggest that spheroidal galaxies have formed by starbursts induced by strong magnetic fields. Then we show that this idea naturally leads to the formation of spheroidal systems only in massive and high-redshift objects in hierarchically clustering universe, giving a simple explanation for various observations.Comment: 7 pages including 2 figures. Accepted by ApJ Letter

Analytical solution of the optimal laser control problem in two-level systems

The optimal control of two-level systems by time-dependent laser fields is studied using a variational theory. We obtain, for the first time, general analytical expressions for the optimal pulse shapes leading to global maximization or minimization of different physical quantities. We present solutions which reproduce and improve previous numerical results.Comment: 12 pages, 2 figure

Realistic lower bounds for the factorization time of large numbers on a quantum computer.

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