The Gelfand map and symmetric products

If A is an algebra of functions on X, there are many cases when X can be regarded as included in Hom(A,C) as the set of ring homomorphisms. In this paper the corresponding results for the symmetric products of X are introduced. It is shown that the symmetric product Sym^n(X) is included in Hom(A,C) as the set of those functions that satisfy equations generalising f(xy)=f(x)f(y). These equations are related to formulae introduced by Frobenius and, for the relevant A, they characterise linear maps on A that are the sum of ring homomorphisms. The main theorem is proved using an identity satisfied by partitions of finite sets.Comment: 14 pages, Late

Signals of R-parity violating supersymmetry in neutrino scattering at muon storage rings

Neutrino oscillation signals at muon storage rings can be faked by supersymmetric (SUSY) interactions in an R-parity violating scenario. We investigate the $\tau$-appearance signals for both long-baseline and near-site experiments, and conclude that the latter is of great use in distinguishing between oscillation and SUSY effects. On the other hand, SUSY can cause a manifold increase in the event rate for wrong-sign muons at a long-baseline setting, thereby providing us with signatures of new physics.Comment: 7 pages LaTeX, 4 ps figures, accepted for publication in Phys. Rev.

On the nature of the near-UV extended light in Seyfert galaxies

We study the nature of the extended near-UV emission in the inner kiloparsec of a sample of 15 Seyfert galaxies which have both near-UV (F330W) and narrow band [OIII] high resolution Hubble images. For the majority of the objects we find a very similar morphology in both bands. From the [OIII] images we construct synthetic images of the nebular continuum plus the emission line contribution expected through the F330W filter, which can be subtracted from the F330W images. We find that the emission of the ionised gas dominates the near-UV extended emission in half of the objects. A further broad band photometric study, in the bands F330W (U), F547M (V) and F160W (H), shows that the remaining emission is dominated by the underlying galactic bulge contribution. We also find a blue component whose nature is not clear in 4 out of 15 objects. This component may be attributed to scattered light from the AGN, to a young stellar population in unresolved star clusters, or to early-disrupted clusters. Star forming regions and/or bright off-nuclear star clusters are observed in 4/15 galaxies of the sample.Comment: 23 pages, 6 figures, 3 tables; accepted for publication in MNRA

On the massless "just-so" solution to the solar neutrino problem

We study the effect of the non-resonant, vacuum oscillation-like neutrino flavor conversion induced by non-standard flavor changing and non-universal flavor diagonal neutrino interactions with electrons in the sun. We have found an acceptable fit for the combined analysis for the solar experiments total rates, the Super-Kamiokande (SK) energy spectrum and zenith angle dependence. Phenomenological constraints on non-standard flavor changing and non-universal flavor diagonal neutrino interactions are considered.Comment: 4 pages, Latex, uses eps

Measuring the Density Matrix by Local Addressing

We introduce a procedure to measure the density matrix of a material system. The density matrix is addressed locally in this scheme by applying a sequence of delayed light pulses. The procedure is based on the stimulated Raman adiabatic passage (STIRAP) technique. It is shown that a series of population measurements on the target state of the population transfer process yields unambiguous information about the populations and coherences of the addressed states, which therefore can be determined.Comment: 4 pages, 1 figur

Lepton number violating interactions and their effects on neutrino oscillation experiments

Mixing between bosons that transform differently under the standard model gauge group, but identically under its unbroken subgroup, can induce interactions that violate the total lepton number. We discuss four-fermion operators that mediate lepton number violating neutrino interactions both in a model-independent framework and within supersymmetry (SUSY) without R-parity. The effective couplings of such operators are constrained by: i) the upper bounds on the relevant elementary couplings between the bosons and the fermions, ii) by the limit on universality violation in pion decays, iii) by the data on neutrinoless double beta decay and, iv) by loop-induced neutrino masses. We find that the present bounds imply that lepton number violating neutrino interactions are not relevant for the solar and atmospheric neutrino problems. Within SUSY without R-parity also the LSND anomaly cannot be explained by such interactions, but one cannot rule out an effect model-independently. Possible consequences for future terrestrial neutrino oscillation experiments and for neutrinos from a supernova are discussed.Comment: 28 pages, 2 figures, Late

Neutrino Anomalies without Oscillations

I review explanations for the three neutrino anomalies (solar, atmospheric and LSND) which go beyond the ``conventional'' neutrino oscillations induced by mass-mixing. Several of these require non-zero neutrino masses as well.Comment: 14pages, LATEX format, 3 figure

An Atlas of the circumnuclear regions of 75 Seyfert galaxies in the near-UV with HST Advanced Camera for Surveys

We present an atlas of the central regions of 75 Seyfert galaxies imaged in the near-UV with the Advanced Camera for Surveys of the Hubble Space Telescope at an average resolution of ~10pc. These data complement archival high resolution data from the Space Telescope at optical and near-IR wavelengths, creating an extremely valuable dataset for astronomers with a broad range of scientific interests. Our goal is to investigate the nature of the near-UV light in these objects, its relation to the circumnuclear starburst phenomenon, and the connection of this to the evolution and growth of the galaxy bulge and central black hole. In this paper, we describe the near-UV morphology of the objects and characterize the near-UV emission. We estimate the size and the luminosity of the emitting regions and extract the luminosity profile. We also determine the presence of unresolved compact nuclei. In addition, the circumnuclear stellar cluster population is identified, and the contribution of the stellar clusters to the total light, at this wavelength, is estimated. The size of the sample allows us to draw robust statistical conclusions. We find that {Seyfert 1} galaxies are completely dominated by its bright and compact nucleus, that remains point-like at this resolution, while we find almost no unresolved nucleus in Seyfert 2. The Seyfert types 1 and 2 are quite segregated in an asymmetry vs compactness plot. Stellar clusters are found somewhat more frequently in Sy2 (in ~70% of the galaxies) than in Sy1 (~57%), and contribute more to the total light in Sy2, but this two differences seem to be mostly due to the large contribution of the compact nucleus in Sy1, as the luminosity distribution of the clusters is similar in both Sy types.Comment: Accepted for publication in AJ, 58 pages, 20 figures. High-resolution figures for all the objects are available at http://www.iaa.es/~manuel/publications/paper01.htm

Embedding variables in finite dimensional models

Global problems associated with the transformation from the Arnowitt, Deser and Misner (ADM) to the Kucha\v{r} variables are studied. Two models are considered: The Friedmann cosmology with scalar matter and the torus sector of the 2+1 gravity. For the Friedmann model, the transformations to the Kucha\v{r} description corresponding to three different popular time coordinates are shown to exist on the whole ADM phase space, which becomes a proper subset of the Kucha\v{r} phase spaces. The 2+1 gravity model is shown to admit a description by embedding variables everywhere, even at the points with additional symmetry. The transformation from the Kucha\v{r} to the ADM description is, however, many-to-one there, and so the two descriptions are inequivalent for this model, too. The most interesting result is that the new constraint surface is free from the conical singularity and the new dynamical equations are linearization stable. However, some residual pathology persists in the Kucha\v{r} description.Comment: Latex 2e, 29 pages, no figure

Two-photon linewidth of light "stopping" via electromagnetically induced transparency

We analyze the two-photon linewidth of the recently proposed adiabatic transfer technique for ``stopping'' of light using electromagnetically induced transparency (EIT). We shown that a successful and reliable transfer of excitation from light to atoms and back can be achieved if the spectrum of the input probe pulse lies within the initial transparency window of EIT, and if the two-photon detuning $\delta$ is less than the collective coupling strength (collective vacuum Rabi-frequency) $g\sqrt{N}$ divided by $\sqrt{\gamma T}$, with $\gamma$ being the radiative decay rate, $N$ the effective number of atoms in the sample, and $T$ the pulse duration. Hence in an optically thick medium light ``storage'' and retrieval is possible with high fidelity even for systems with rather large two-photon detuning or inhomogeneous broadening.Comment: 2 figure