When renormalizability is not sufficient: Coulomb problem for vector bosons

The Coulomb problem for vector bosons W incorporates a known difficulty; the boson falls on the center. In QED the fermion vacuum polarization produces a barrier at small distances which solves the problem. In a renormalizable SU(2) theory containing vector triplet (W^+,W^-,gamma) and a heavy fermion doublet F with mass M the W^- falls on F^+, to distances r ~ 1/M, where M can be made arbitrary large. To prevent the collapse the theory needs additional light fermions, which switch the ultraviolet behavior of the theory from the asymptotic freedom to the Landau pole. Similar situation can take place in the Standard Model. Thus, the renormalizability of a theory is not sufficient to guarantee a reasonable behavior at small distances for non-perturbative problems, such as a bound state problem.Comment: Four page

Flux- and volume-limited groups/clusters for the SDSS galaxies: catalogues and mass estimation

We provide flux-limited and volume-limited galaxy group and cluster catalogues, based on the spectroscopic sample of the SDSS data release 10 galaxies. We used a modified friends-of-friends (FoF) method with a variable linking length in the transverse and radial directions to identify as many realistic groups as possible. The flux-limited catalogue incorporates galaxies down to m_r = 17.77 mag. It includes 588193 galaxies and 82458 groups. The volume-limited catalogues are complete for absolute magnitudes down to M_r = -18.0, -18.5, -19.0, -19.5, -20.0, -20.5, and -21.0; the completeness is achieved within different spatial volumes, respectively. Our analysis shows that flux-limited and volume-limited group samples are well compatible to each other, especially for the larger groups/clusters. Dynamical mass estimates, based on radial velocity dispersions and group extent in the sky, are added to the extracted groups. The catalogues can be accessed via http://cosmodb.to.ee and the Strasbourg Astronomical Data Center (CDS).Comment: 16 pages, 18 figures, 2 tables, accepted for publication in A&

A generalized Ramsey excitation scheme with suppressed light shift

We experimentally investigate a recently proposed optical excitation scheme [V.I. Yudin et al., Phys. Rev. A 82, 011804(R)(2010)] that is a generalization of Ramsey's method of separated oscillatory fields and consists of a sequence of three excitation pulses. The pulse sequence is tailored to produce a resonance signal which is immune to the light shift and other shifts of the transition frequency that are correlated with the interaction with the probe field. We investigate the scheme using a single trapped 171Yb+ ion and excite the highly forbidden 2S1/2-2F7/2 electric-octupole transition under conditions where the light shift is much larger than the excitation linewidth, which is in the Hertz range. The experiments demonstrate a suppression of the light shift by four orders of magnitude and an immunity against its fluctuations.Comment: 5 pages, 4 figure

Cherenkov radiation by particles traversing the background radiatio n

High energy particles traversing the Universe through the cosmic microwave backgroung radiation can, in principle, emit Cherenkov radiation. It is shown that the energy threshold for this radiation is extremely high and its intensity would be too low due to the low density of the "relic photons gas" and very weak interaction of two photons.Comment: 6 pages, LATEX, no Figs.; to be published in JETP Lett. 75 (N4) (2002

The role of energy-momentum conservation in emission of Cherenkov gluons

The famous formula for the emission angle of Cherenkov radiation should be modified when applied to hadronic reactions because of recoil effects. They impose the upper limit on the energy of the gluon emitted at a given angle. Also, it leads to essential corrections to the nuclear refractive index value as determined from the angular position of Cherenkov rings.Comment: 6

Charge density of a positively charged vector boson may be negative

The charge density of vector particles, for example W, may change sign. The effect manifests itself even for a free propagation; when the energy of the W-boson is higher than sqrt{2}m and the standing-wave is considered the charge density oscillates in space. The charge density of W also changes sign in close vicinity of a Coulomb center. The dependence of this effect on the g-factor for an arbitrary vector boson, for example rho-meson, is discussed. An origin of this surprising effect is traced to the electric quadrupole moment and spin-orbit interaction of vector particles. Their contributions to the current have a polarization nature. The charge density of this current, rho = -\nabla \cdot P, where P is an effective polarization vector that depends on the quadrupole moment and spin-orbit interaction, oscillates in space, producing zero contribution to the total charge.Comment: 4 pages, revte

Vacuum Cherenkov radiation

Within the classical Maxwell-Chern-Simons limit of the Standard-Model Extension (SME), the emission of light by uniformly moving charges is studied confirming the possibility of a Cherenkov-type effect. In this context, the exact radiation rate for charged magnetic point dipoles is determined and found in agreement with a phase-space estimate under certain assumptions.Comment: 4 pages, REVTeX