3,796 research outputs found
The Supersymmetric Stueckelberg Mass and Overcoming the Fayet-Iliopoulos Mechanism for Breaking Symmetry
Gauge invariant generation of mass for supersymmetric U(1) vector field
through use of a chiral Stueckelberg superfield is considered. When a
Fayet-Iliopoulos D term is also present, no breaking of supersymmetry ever
occurs so long as the Stueckelberg mass is not zero. A moduli space in which
gauge symmetry is spontaneously broken arises in this case
GZK photons as UHECR above 10 eV
"GZK photons" are produced by extragalactic nucleons through the resonant
photoproduction of pions. We present the expected range of the GZK photon
fraction of UHECR, assuming a particular UHECR spectrum and primary nucleons,
and compare it with the minimal photon fraction predicted by Top-Down models.Comment: Talk given at TAUP2005, Sept. 10-14 2005, Zaragoza (Spain); 3 pages,
2 figure
Unstable superheavy relic particles as a source of neutrinos responsible for the ultrahigh-energy cosmic rays
Decays of superheavy relic particles may produce extremely energetic
neutrinos. Their annihilations on the relic neutrinos can be the origin of the
cosmic rays with energies beyond the Greisen-Zatsepin-Kuzmin cutoff. The red
shift acts as a cosmological filter selecting the sources at some particular
value z_e, for which the present neutrino energy is close to the Z pole of the
annihilation cross section. We predict no directional correlation of the
ultrahigh-energy cosmic rays with the galactic halo. At the same time, there
can be some directional correlations in the data, reflecting the distribution
of matter at red shift z=z_e. Both of these features are manifest in the
existing data. Our scenario is consistent with the neutrino mass reported by
Super-Kamiokande and requires no lepton asymmetry or clustering of the
background neutrinos.Comment: 3 pages, revtex; references adde
UHECR Particle Spectra from Crypton Decays
We calculate the spectra of ultra-high-energy cosmic rays (UHECRs) in an
explicit top-down model based on the decays of metastable neutral `crypton'
states in a flipped SU(5) string model. For each of the eight specific
10th-order superpotential operators that might dominate crypton decays, we
calculate the spectra of both protons and photons, using a code incorporating
supersymmetric evolution of the injected spectra. For all the decay operators,
the total UHECR spectra are compatible with the available data. Also, the
fractions of photons are compatible with all the published upper limits, but
may be detectable in future experiments.Comment: 9 pages latex, 10 eps figure
Comments on ``A note on first-order formalism and odd-derivative actions'' by S. Deser
We argue that the obstacles to having a first-order formalism for
odd-derivative actions presented in a pedagogical note by Deser are based on
examples which are not first-order forms of the original actions. The general
derivation of an equivalent first-order form of the original second-order
action is illustrated using the example of topologically massive
electrodynamics (TME). The correct first-order formulations of the TME model
keep intact the gauge invariance presented in its second-order form
demonstrating that the gauge invariance is not lost in the Ostrogradsky
process.Comment: 6 pages, references are adde
Bouncing surface plasmons
Employing an interferometric cavity ring-down technique we study the launching, propagation and reflection of surface plasmons on a smooth gold-air interface that is intersected by two parallel, subwavelength wide slits. Inside the low-finesse optical cavity defined by these slits the surface plasmon is observed to make multiple bounces. Our experimental data allow us to determine the surface-plasmon group velocity (vgroup = 2.7±0.3×10?8 m/s at l = 770 nm) and the reflection coefficient (R ? 0.04) of each of our slits for an incident surface plasmon. Moreover, we find that the phase jump upon reflection off a slit is equal to the scattering phase acquired when light is converted into a plasmon at one slit and back-converted to light at the other slit. This allows us to explain fine details in the transmission spectrum of our double slits
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