1,537 research outputs found
Control of quantum fluctuations for a Yukawa interaction in the Kaluza Klein picture
We study a system of fermions interacting with a scalar field, in 4+1
dimensions where the 5th dimension is compactified, using an exact functional
method, where quantum fluctuations are controlled by the amplitude of the bare
fermion mass. The integration of our equationsleads to the properties of the
dressed Yukawa coupling, that we study at one-loop so as to show the
consistency of the approach. Beyond one loop, the non-perturbative aspect of
the method gives us the possibility to derive the dynamical fermion mass. The
result obtained is cut off independent and this derivation proposes an
alternative to the Schwinger-Dyson approach.Comment: extended discussion on the scalar effective potentia
On Scattering of Electromagnetic Waves by a Wormhole
We consider scattering of a plane electromagnetic wave by a wormhole. It is
found that the scattered wave is partially depolarized and has a specific
interference picture depending on parameters of the wormhole and the distance
to the observer. It is proposed that such features can be important in the
direct search of wormholes
Soliton solutions of the non-linear Schroedinger equation with nonlocal Coulomb and Yukawa-interactions
We study the non-linear Schroedinger equation in (1+1) dimensions in which
the nonlinear term is taken in the form of a nonlocal interaction of the
Coulomb or Yukawa-type.
We solve the equation numerically and find that, for all values of the
nonlocal coupling constant, and in all cases, the equation possesses solitonic
solutions. We show that our results, for the dependence of the height of the
soliton on the coupling constant, are in good agreement with the predictions
based on an analytic treatment in which the soliton is approximated by a
gaussian.Comment: 8 pages including 4 eps figure
Pursuing interpretations of the HERA large-Q2 data
We explore interpretations of the anomaly observed by H1 and ZEUS at HERA in
deep-inelastic e^+ p scattering at very large Q^2. We discuss the possibilities
of new effective interactions and the production of a narrow state of mass 200
GeV with leptoquark couplings. We compare these models with the measured Q^2
distributions: for the contact terms, constraints from LEP2 and the Tevatron
allow only a few choices of helicity and flavour structure that could roughly
fit the HERA data. The data are instead quite consistent with the Q^2
distribution expected from a leptoquark state. We study the production cross
sections of such a particle at the Tevatron and at HERA. The absence of a
signal at the Tevatron disfavours the likelihood that any such leptoquark
decays only into e^+ q. We then focus on the possibility that the leptoquark is
a squark with R-violating couplings. In view of the present experimental limits
on such couplings, the most likely production channels are e^+d -> scharm_L or
perhaps e^+d->stop, with e^+s->stop a more marginal possibility. Possible tests
of our preferred model include the absence both of analogous events in e^- p
collisions and of charged current events, and the presence of detectable
cascade decays whose kinematical signatures we discuss. We also discuss the
possible implications for K->pi nu nubar, neutrinoless double-beta decay, the
Tevatron and for e^+ e^- ->q qbar and neutralinos at LEP2.Comment: 28 pages, Latex, epsfig, 8 figures. Note added on contact term
Evidence for right-handed neutrinos at a neutrino factory
We emphasize that a muon based neutrino factory could show the existence of
light right-handed neutrinos, if a deficit in the number of detected events is
observed at a near detector. This could be as large as ~10% if the size of the
new interactions saturates the present limits from electroweak precision data,
what is not excluded by the oscillation experiments performed up to now. A
simple model realizing such a scenario can be obtained adding right-handed
neutrinos to the minimal Standard Model, together with an extra scalar doublet
and a triplet of hypercharge 1. In this case, however, the possible deficit is
reduced by a factor of ~3, and the Yukawa couplings must be adequately chosen.
This is also generically required if lepton flavour violation must be below
present bounds.Comment: Latex 18 pages, 2 eps figure
Interactive Threshold Mercurial Signatures and Applications
Equivalence class signatures allow a controlled form of malleability based on equivalence classes defined over the message space. As a result, signatures can be publicly randomized and adapted to a new message representative in the same equivalence class. Notably, security requires that an adapted signature-message pair looks indistinguishable from a random signature-message pair in the space of valid signatures for the new message representative. Together with the decisional Diffie-Hellman assumption, this yields an unlinkability notion (class-hiding), making them a very attractive building block for privacy-preserving primitives.
Mercurial signatures are an extension of equivalence class signatures that allow malleability for the key space. Unfortunately, the most efficient construction to date suffers a severe limitation that limits their application: only a weak form of public key class-hiding is supported. In other words, given knowledge of the original signing key and randomization of the corresponding public key, it is possible to identify whether they are related.
In this work, we put forth the notion of interactive threshold mercurial signatures and show how they help to overcome the above-mentioned limitation. Moreover, we present constructions in the two-party and multi-party settings, assuming at least one honest signer. We also discuss related applications, including blind signatures, multi-signatures, and threshold ring signatures. To showcase the practicality of our approach, we implement the proposed constructions, comparing them against related alternatives
Phenomenology of Randall-Sundrum Black Holes
We explore the phenomenology of microscopic black holes in the
Randall-Sundrum (RS) model. We consider the canonical framework in which both
gauge and matter fields are confined to the brane and only gravity spills into
the extra dimension. The model is characterized by two parameters, the mass of
the first massive graviton , and the curvature of the RS
anti-de Sitter space. We compute the sensitivity of present and future cosmic
ray experiments to various regions of and and compare with that
of Runs I and II at the Tevatron. As part of our phenomenological analysis, we
examine constraints placed on by AdS/CFT considerations.Comment: Version to appear in Physical Review D; contains additional analysis
on sensitivity of OW
Direct test of time-reversal symmetry in the entangled neutral kaon system at a -factory
We present a novel method to perform a direct T (time reversal) symmetry test
in the neutral kaon system, independent of any CP and/or CPT symmetry tests.
This is based on the comparison of suitable transition probabilities, where the
required interchange of in out states for a given process is obtained
exploiting the Einstein-Podolsky-Rosen correlations of neutral kaon pairs
produced at a -factory. In the time distribution between the two decays,
we compare a reference transition like the one defined by the time ordered
decays with the T -conjugated one defined by . With the use of this and other T conjugated comparisons, the KLOE-2
experiment at DANE could make a significant test
Holographic approach to a minimal Higgsless model
In this work, following an holographic approach, we carry out a low energy
effective study of a minimal Higgsless model based on SU(2) bulk symmetry
broken by boundary conditions, both in flat and warped metric. The holographic
procedure turns out to be an useful computation technique to achieve an
effective four dimensional formulation of the model taking into account the
corrections coming from the extra dimensional sector. This technique is used to
compute both oblique and direct contributions to the electroweak parameters in
presence of fermions delocalized along the fifth dimension.Comment: Latex file, 23 page
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