Generation of Cosmological Seed Magnetic Fields from Inflation with Cutoff

Inflation has the potential to seed the galactic magnetic fields observed today. However, there is an obstacle to the amplification of the quantum fluctuations of the electromagnetic field during inflation: namely the conformal invariance of electromagnetic theory on a conformally flat underlying geometry. As the existence of a preferred minimal length breaks the conformal invariance of the background geometry, it is plausible that this effect could generate some electromagnetic field amplification. We show that this scenario is equivalent to endowing the photon with a large negative mass during inflation. This effective mass is negligibly small in a radiation and matter dominated universe. Depending on the value of the free parameter of the theory, we show that the seed required by the dynamo mechanism can be generated. We also show that this mechanism can produce the requisite galactic magnetic field without resorting to a dynamo mechanism.Comment: Latex, 16 pages, 2 figures, 4 references added, minor corrections; v4: more references added, boundary term written in a covariant form, discussion regarding other gauge fields added, submitted to PRD; v5: matched with the published versio

The JCMT 12CO(3-2) Survey of the Cygnus X Region: I. A Pathfinder

Cygnus X is one of the most complex areas in the sky. This complicates interpretation, but also creates the opportunity to investigate accretion into molecular clouds and many subsequent stages of star formation, all within one small field of view. Understanding large complexes like Cygnus X is the key to understanding the dominant role that massive star complexes play in galaxies across the Universe. The main goal of this study is to establish feasibility of a high-resolution CO survey of the entire Cygnus X region by observing part of it as a Pathfinder, and to evaluate the survey as a tool for investigating the star-formation process. A 2x4 degree area of the Cygnus X region has been mapped in the 12CO(3-2) line at an angular resolution of 15" and a velocity resolution of ~0.4km/s using HARP-B and ACSIS on the James Clerk Maxwell Telescope. The star formation process is heavily connected to the life-cycle of the molecular material in the interstellar medium. The high critical density of the 12CO(3-2) transition reveals clouds in key stages of molecule formation, and shows processes that turn a molecular cloud into a star. We observed ~15% of Cygnus X, and demonstrated that a full survey would be feasible and rewarding. We detected three distinct layers of 12CO(3-2) emission, related to the Cygnus Rift (500-800 pc), to W75N (1-1.8 kpc), and to DR21 (1.5-2.5 kpc). Within the Cygnus Rift, HI self-absorption features are tightly correlated with faint diffuse CO emission, while HISA features in the DR21 layer are mostly unrelated to any CO emission. 47 molecular outflows were detected in the Pathfinder, 27 of them previously unknown. Sequentially triggered star formation is a widespread phenomenon.Comment: 18 pages, 13 figures, accepted for publication in Astronomy & Astrophysic

Emergence of a Twisted Magnetic Flux Bundle as a Source of Strong Flare Activity

Sunspot proper motions and flares of a super active region NOAA 5395, which was the biggest and the most flare-active region in the 22nd sunspot cycle, were analyzed in details. We measured sunspot proper motions by using the H-alpha - 5.0 A images obtained with the 60-cm Domeless Solar Telescope (DST) at Hida Observatory, Kyoto University and found some peculiar vortex-like motions of small satellite spots successively emerged from the leading edge of this sunspot group. To explain these motions of small sunspots, we proposed a schematic model of the successive emergence of twisted and winding magnetic flux ropes coiling around a trunk of magnetic flux tube. The location of the strongest flare activity was found to coincide with very the site of the vortex-like motions of sunspots. We conclude that the flare-productive magnetic shear is produced by the emergence of the twisted magnetic flux bundle. Magnetic energy is stored in the twisted flux tubes which are originally formed in the convection zone and released as flares in the course of the emergence of the twisted flux tubes above the photosphere.Comment: 19 pages LaTeX, 8 figures, ApJ accepted high resolution figures : e-mail to [email protected]

Devil Facial Tumor Disease, A Potential Model of the Cancer Stem-Cell Process?

Tasmanian devil facial tumor disease (DFTD) is a naturally occurring contagious cancer which is transmitted as a clonal cell line between devils. The malignant cell line evolved from a Schwann cell or precursor prior to 1996 and since then has undergone continuous division without exhausting its replicative potential, suggesting a profound capacity for self renewal. It is therefore important to elucidate whether DFTD may have a stem cell origin. Deciphering the pathways regulating DFT cell proliferation and survival could lead to increased understanding of this transimissible cancer and to the development of successful therapies to halt the disease. We investigated whether DFT cells have originated from transformed stem cells by measuring the expression levels of thirteen genes characteristic to embryonic stem and/or pluripotent germ cells. No differences in gene expression were observed between DFT cells and peripheral nerve controls, and therefore our results provide additional support for Schwann cell or peripheral nerve origin of DFTD. Although our dataset is preliminary, it does not suggest that DFTs have cancer stem cells (CSCs) origin. We provide details of further experiments needed to ultimately confirm the role of cancer stem cells in DFTD progression

On a mechanism for enhancing magnetic activity in tidally interacting binaries

We suggest a mechanism for enhancing magnetic activity in tidally interacting binaries. We suppose that the deviation of the primary star from spherical symmetry due to the tidal influence of the companion leads to stellar pulsation in its fundamental mode. It is shown that stellar radial pulsation amplifies torsional Alfv{\'e}n waves in a dipole-like magnetic field, buried in the interior, according to the recently proposed swing wave-wave interaction (Zaqarashvili 2001). Then amplified Alfv{\'e}n waves lead to the onset of large-scale torsional oscillations, and magnetic flux tubes arising towards the surface owing to magnetic buoyancy diffuse into the atmosphere producing enhanced chromospheric and coronal emission.Comment: Accepted in Ap

Origin of Magnetic Fields in the Universe Due to Nonminimal Gravitational-Electromagnetic Coupling

Basically the only existing theories for the creation of a magnetic field B in the Universe are the creation of a seed field of order 10^{-20} G in spiral galaxy which is subsequently supposedly amplified up to the observed 10^{-6} - 10^{-5} G by a dynamo process or a seed intergalactic field of magnitude 10^{-12} - 10^{-10} G which is amplified by collapse and differential rotation. No satisfactory dynamo theory, however, exists today. We show that a 10^{-6} - 10^{-5} G magnetic field in spiral galaxies is directly obtained from a nonminimal gravitational-electromagnetic coupling, without the need of significant dynamo amplification.Comment: 5 pages, Latex (Revtex), no figures, To appear in PR

Nonlinear electrodynamics and CMB polarization

Recently WMAP and BOOMERanG experiments have set stringent constraints on the polarization angle of photons propagating in an expanding universe: $\Delta \alpha = (-2.4 \pm 1.9)^\circ$. The polarization of the Cosmic Microwave Background radiation (CMB) is reviewed in the context of nonlinear electrodynamics (NLED). We compute the polarization angle of photons propagating in a cosmological background with planar symmetry. For this purpose, we use the Pagels-Tomboulis (PT) Lagrangian density describing NLED, which has the form $L\sim (X/\Lambda^4)^{\delta - 1}\; X$, where $X=1/4 F_{\alpha\beta} F^{\alpha \beta}$, and $\delta$ the parameter featuring the non-Maxwellian character of the PT nonlinear description of the electromagnetic interaction. After looking at the polarization components in the plane orthogonal to the ($x$)-direction of propagation of the CMB photons, the polarization angle is defined in terms of the eccentricity of the universe, a geometrical property whose evolution on cosmic time (from the last scattering surface to the present) is constrained by the strength of magnetic fields over extragalactic distances.Comment: 17 pages, 2 figures, minor changes, references adde

Constraining the Magnetic Effects on HI Rotation Curves and the Need for Dark Halos

The density profiles of dark halos are usually inferred from the rotation curves of disk galaxies based on the assumption that the gas is a good tracer of the gravitational potential of the galaxies. Some authors have suggested that magnetic pinching forces could alter significantly the rotation curves of spiral galaxies. In contrast to other studies which have concentrated in the vertical structure of the disk, here we focus on the problem of magnetic confinement in the radial direction to bound the magnetic effects on the HI rotation curves. It is shown that azimuthal magnetic fields can hardly speed up the HI disk of galaxies as a whole. In fact, based on virial constraints we show that the contribution of galactic magnetic fields to the rotation curves cannot be larger than ~10 km/s at the outermost point of HI detection, if the galaxies did not contain dark matter at all, and up to 20 km/s in the conventional dark halo scenario. The procedure to estimate the maximum effect of magnetic fields is general and applicable to any particular galaxy disk. The inclusion of the surface terms, namely the intergalactic (thermal, magnetic or ram) pressure, does not change our conclusions. Other problems related with the magnetic alternative to dark halos are highlighted. The relevance of magnetic fields in the cuspy problem of dark halos is also discussed.Comment: 12 pages, 1 figure, accepted for publication in The Astrophysical Journa