3,456 research outputs found
A Simple UV-Completion of QED in 5D
We construct a Lifshitz-like version of five-dimensional (5D) QED which is UV
- completed and reduces at low energies to ordinary 5D QED. The UV quantum
behaviour of this theory is very smooth. In particular, the gauge coupling
constant is finite at all energy scales and at all orders in perturbation
theory. We study the IR properties of this theory, when compactified on a
circle, and compare the one-loop energy dependence of the coupling in the
Lifshitz theory with that coming from the standard 5D QED effective field
theory. The range of validity of the 5D effective field theory is found to
agree with the more conservative version of Naive Dimensional Analysis.Comment: 24 pages, 7 figures; v2: Minor improvements, matches journal versio
Massless radiation from Strings: quantum spectrum average statistics and cusp-kink configurations
We derive general formulae for computing the average spectrum for Bosonic or
Fermionic massless emission from generic or particular sets of closed
superstring quantum states, among the many occurring at a given large value of
the number operator. In particular we look for states that can produce a
Bosonic spectrum resembling the classical spectrum expected for peculiar
cusp-like or kink-like classical configurations, and we perform a statistical
counting of their average number. The results can be relevant in the framework
of possible observations of the radiation emitted by cosmic strings.Comment: 13 pages, 4 figures, improved explanations, an appendix added on
rotating folded strin
Fermion Mass Hierarchy in Lifshitz Type Gauge Theory
We study the origin of fermion mass hierarchy and flavor mixing in a Lifshitz
type extension of the standard model including an extra scalar field. We show
that the hierarchical structure can originate from renormalizable interactions.
In contrast to the Froggatt-Nielsen mechanism, the higher the dimension of
associated operators, the heavier the fermion masses. Tiny masses for
left-handed neutrinos are obtained without introducing right-handed neutrinos.Comment: 13 pages; clarifications of some point
Effect of sodium hyluronate added to topical corticosteroids in chronic rhinosinusitis with nasal polyposis
Available medical treatments for chronic rhinosinusitis (CRS) with nasal polyposis (CRSwNP) comprise systemic and topical therapies. Although topical corticosteroids are effective in the treatment of CRS, they are not completely devoid of adverse effects. Thus, care has to be taken when long-term treatments are prescribed. There is recent evidence that sodium hyaluronate (SH), the major component of many extracellular matrices, promotes tissue healing, including activation and moderation of the inflammatory responses, cell proliferation, migration, and angiogenesis
Black hole - D-brane correspondence: An example
We explore the connection between D-branes and black holes in one particular
case: a -brane compactified to four dimensions on . Using the
-brane boundary state description we show the equivalence with a double
extremal N=2 black hole solution of four dimensional supergravity.Comment: 15 pages, LaTeX. Contribution by C. Nunez to the conference Quantum
Gravity in the Southern Cone, Bariloche 7-10 January 1998; to appear in the
proceeding
Vortex Quantum Nucleation and Tunneling in Superconducting Thin Films: Role of Dissipation and Periodic Pinning
We investigate the phenomenon of decay of a supercurrent in a superconducting
thin film in the absence of an applied magnetic field. The resulting
zero-temperature resistance derives from two equally possible mechanisms: 1)
quantum tunneling of vortices from the edges of the sample; and 2) homogeneous
quantum nucleation of vortex-antivortex pairs in the bulk of the sample,
arising from the instability of the Magnus field's ``vacuum''. We study both
situations in the case where quantum dissipation dominates over the inertia of
the vortices. We find that the vortex tunneling and nucleation rates have a
very rapid dependence on the current density driven through the sample.
Accordingly, whilst normally the superconductor is essentially resistance-free,
for the high current densities that can be reached in high- films a
measurable resistance might develop. We show that edge-tunneling appears
favoured, but the presence of pinning centres and of thermal fluctuations leads
to an enhancement of the nucleation rates. In the case where a periodic pinning
potential is artificially introduced in the sample, we show that
current-oscillations will develop indicating an effect specific to the
nucleation mechanism where the vortex pair-production rate, thus the
resistance, becomes sensitive to the corrugation of the pinning substrate. In
all situations, we give estimates for the observability of the studied
phenomena.Comment: 8 pages (LaTeX), 2 postscript figures. Invited talk to the SATT8 (8th
Italian Meeting on High-T_c Superconductivity), Como (Italy), Villa Olmo, 1-4
October 1996, to be published in La Rivista del Nuovo Cimento
Electromagnetism and multiple-valued loop-dependent wave functionals
We quantize the Maxwell theory in the presence of a electric charge in a
"dual" Loop Representation, i.e. a geometric representation of magnetic
Faraday's lines. It is found that the theory can be seen as a theory without
sources, except by the fact that the wave functional becomes multivalued. This
can be seen as the dual counterpart of what occurs in Maxwell theory with a
magnetic pole, when it is quantized in the ordinary Loop Representation. The
multivaluedness can be seen as a result of the multiply-connectedness of the
configuration space of the quantum theory.Comment: 5 page
Quantum Oscillator on \DC P^n in a constant magnetic field
We construct the quantum oscillator interacting with a constant magnetic
field on complex projective spaces \DC P^N, as well as on their non-compact
counterparts, i. e. the dimensional Lobachewski spaces . We
find the spectrum of this system and the complete basis of wavefunctions.
Surprisingly, the inclusion of a magnetic field does not yield any qualitative
change in the energy spectrum. For the magnetic field does not break the
superintegrability of the system, whereas for N=1 it preserves the exact
solvability of the system.
We extend this results to the cones constructed over \DC P^N and , and perform the (Kustaanheimo-Stiefel) transformation of these systems
to the three-dimensional Coulomb-like systems.Comment: 9 pages, 1 figur
String Form Factors
We compute the cross section for scattering of light string probes by
randomly excited closed strings. For high energy probes, the cross section
factorizes and can be used to define effective form factors for the excited
targets. These form factors are well defined without the need for infinite
subtractions and contain information about the shape and size of typical
strings. For highly excited strings the elastic form factor can be written in
terms of the `plasma dispersion function', which describes charge screening in
high temperature plasmas.Comment: 18 pages, 3 figures. Typos corrected, 1 footnote (in Section 4) and 1
reference adde
Edge Tunneling of Vortices in Superconducting Thin Films
We investigate the phenomenon of the decay of a supercurrent due to the
zero-temperature quantum tunneling of vortices from the edge in a thin
superconducting film in the absence of an external magnetic field. An explicit
formula is derived for the tunneling rate of vortices, which are subject to the
Magnus force induced by the supercurrent, through the Coulomb-like potential
barrier binding them to the film's edge. Our approach ensues from the
non-relativistic version of a Schwinger-type calculation for the decay of the
2D vacuum previously employed for describing vortex-antivortex pair-nucleation
in the bulk of the sample. In the dissipation-dominated limit, our explicit
edge-tunneling formula yields numerical estimates which are compared with those
obtained for bulk-nucleation to show that both mechanisms are possible for the
decay of a supercurrent.Comment: REVTeX file, 15 pages, 1 Postscript figure; to appear in Phys.Rev.
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