190 research outputs found
Possible test for CPT invariance with correlated neutral B decays
We study breakdown of symmetry which can occur in the decay process with being a CP eigenstate. In this process, the
standard model expectations for time ordered semi-leptonic and hadronic events,
i.e. which of the two decays takes place first, can be altered in the case that
there is a violation of the symmetry. To illustrate this possibility, we
identify and study several time integrated observables. We find that an
experiment with pairs, has the capability for improving the
bound on violating parameter or perhaps observe violation.Comment: Revised version to be published in PR
Spontaneous Breaking of Lorentz Invariance
We describe how a stable effective theory in which particles of the same
fermion number attract may spontaneously break Lorentz invariance by giving
non-zero fermion number density to the vacuum (and therefore dynamically
generating a chemical potential term). This mecanism yields a finite vacuum
expectation value could relate to work on signals of Lorentz violation
in electrodynamics.Comment: revtex4, 11 pages, 5 figures; v2:references added; v3:more references
added, typos fixed, some points in sect. IV clarified; v4:even more
references added, discussion in sect. V extended; v5:replaced to match
published version (minor corrections of form
On the exact Foldy-Wouthuysen transformation for a Dirac spinor in torsion and other CPT and Lorentz violating backgrounds
We discuss the possibility to perform and use the exact Foldy-Wouthuysen
transformation (EFWT) for the Dirac spinor coupled to different CPT and Lorentz
violating terms. The classification of such terms is performed, selecting those
of them which admit EFWT. For the particular example of an axial vector field,
which can be associated with the completely antisymmetric torsion, we construct
an explicit EFWT in the case when only a timelike component of this axial
vector is present. In the cases when EFWT is not possible, one can still use
the corresponding technique for deriving the perturbative Foldy-Wouthuysen
transformation, as is illustrated in a particular example in the Appendix
Towards Vacuum Superstring Field Theory: The Supersliver
We extend some aspects of vacuum string field theory to superstring field
theory in Berkovits' formulation, and we study the star algebra in the
fermionic matter sector. After clarifying the structure of the interaction
vertex in the operator formalism of Gross and Jevicki, we provide an algebraic
construction of the supersliver state in terms of infinite-dimensional
matrices. This state is an idempotent string field and solves the matter part
of the equation of motion of superstring field theory with a pure ghost BRST
operator. We determine the spectrum of eigenvalues and eigenvectors of the
infinite-dimensional matrices of Neumann coefficients in the fermionic matter
sector. We then analyze coherent states based on the supersliver and use them
in order to construct higher-rank projector solutions, as well as to construct
closed subalgebras of the star algebra in the fermionic matter sector. Finally,
we show that the geometric supersliver is a solution to the superstring field
theory equations of motion, including the (super)ghost sector, with the
canonical choice of vacuum BRST operator recently proposed by Gaiotto,
Rastelli, Sen and Zwiebach.Comment: 45 pages, JHEP styl
D-branes as GMS Solitons in Vacuum String Field Theory
In this paper we map the D-brane projector states in the vacuum string field
theory to the noncommutative GMS solitons based on the recently proposed map of
Witten's star to Moyal's star. We find that the singular geometry conditions of
Moore and Taylor are associated with the commutative modes of these projector
states in our framework. The properties of the candidate closed string state
and the wedge state are also discussed, and the possibility of the non-GMS
soliton in VSFT is commented.Comment: 19 pages, LaTex; revised version, typos corrected; third version, a
new subsection about the midpoint singulariy regularization added;fourth
edition, arguments improve
Baryogenesis from a right-handed neutrino condensate
We show that the baryon asymmetry of the Universe can be generated by a
strongly coupled right handed neutrino condensate which also drives inflation.
The resulting model has only a small number of parameters, which completely
determine not only the baryon asymmetry of the Universe and the mass of the
right handed neutrino but also the inflationary phase. This feature allows us
to make predictions that will be tested by current and planned experiments. As
compared to the usual approach our dynamical framework is both economical and
predictive.Comment: 13 pages, 3 figures. Typos corrected and several points clarified.
Results unchanged. New references adde
Signals for Non-Commutative Interactions at Linear Colliders
Recent theoretical results have demonstrated that non-commutative geometries
naturally appear within the context of string/M-theory. One consequence of this
possibility is that QED takes on a non-abelian nature due to the introduction
of 3- and 4-point functions. In addition, each QED vertex acquires a momentum
dependent phase factor. We parameterize the effects of non-commutative
space-time co-ordinates and show that they lead to observable signatures in
several QED processes in collisions. In particular, we
examine pair annihilation, Moller and Bhabha scattering, as well as
scattering and show that non-commutative scales
of order a TeV can be probed at high energy linear colliders.Comment: 51 pages, 23 figures, typos corrected, figure and references adde
Conservation laws and tachyon potentials in the sliver frame
Conservation laws have provided an elegant and efficient tool to evaluate the
open string field theory interaction vertex, they have been originally
implemented in the case where the string field is expanded in the Virasoro
basis. In this work we derive conservation laws in the case where the string
field is expanded in the so-called sliver -basis. As an
application of these conservation laws derived in the sliver frame, we compute
the open string field action relevant to the tachyon condensation and in order
to present not only an illustration but also an additional information, we
evaluate the action without imposing a gauge choice.Comment: 26 pages, some typos fixed, comments added, references adde
High-energy neutrino conversion and the lepton asymmetry in the universe
We study matter effects on oscillations of high-energy neutrinos in the
Universe. Substantial effect can be produced by scattering of the neutrinos
from cosmological sources (z\gta 1) on the relic neutrino background,
provided that the latter has large CP-asymmetry: \eta\equiv
(n_\nu-n_{\bar{\nu}})/n_\gamma\gta 1, where , and
are the concentrations of neutrinos, antineutrinos and photons. We
consider in details the dynamics of conversion in the expanding neutrino
background. Applications are given to the diffuse fluxes of neutrinos from
GRBs, AGN, and the decay of super-heavy relics. We find that the vacuum
oscillation probability can be modified by and in extreme cases
allowed by present bounds on the effect can reach .
Signatures of matter effects would consist (i) for both active-active and
active-sterile conversion, in a deviation of the numbers of events produced in
a detector by neutrinos of different flavours,
, and of their ratios from the values given by
vacuum oscillations; such deviations can reach , (ii) for
active-sterile conversion, in a characteristic energy dependence of the ratios
. Searches for these matter
effects will probe large CP and lepton asymmetries in the universe.Comment: 32 pages, RevTeX, 16 figures. Substantial changes in the treatment of
conversion effects in the relic neutrino background and of active-active
oscillations of high-energy neutrinos. Figures and references added;
conclusions partially modifie
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