70,408 research outputs found
Fisher matrix forecasts for astrophysical tests of the stability of the fine-structure constant
We use Fisher Matrix analysis techniques to forecast the cosmological impact
of astrophysical tests of the stability of the fine-structure constant to be
carried out by the forthcoming ESPRESSO spectrograph at the VLT (due for
commissioning in late 2017), as well by the planned high-resolution
spectrograph (currently in Phase A) for the European Extremely Large Telescope.
Assuming a fiducial model without variations, we show that ESPRESSO
can improve current bounds on the E\"{o}tv\"{o}s parameter---which quantifies
Weak Equivalence Principle violations---by up to two orders of magnitude,
leading to stronger bounds than those expected from the ongoing tests with the
MICROSCOPE satellite, while constraints from the E-ELT should be competitive
with those of the proposed STEP satellite. Should an variation be
detected, these measurements will further constrain cosmological parameters,
being particularly sensitive to the dynamics of dark energy.Comment: Phys. Lett. B (in press
Meson decay in the Fock-Tani Formalism
The Fock-Tani formalism is a first principle method to obtain effective
interactions from microscopic Hamiltonians. Usually this formalism was applied
to scattering, here we introduced it to calculate partial decay widths for
mesons.Comment: Presented at HADRON05 XI. "International Conference on Hadron
Spectroscopy" Rio de Janeiro, Brazil, August 21 to 26, 200
The Connes-Lott program on the sphere
We describe the classical Schwinger model as a study of the projective
modules over the algebra of complex-valued functions on the sphere. On these
modules, classified by , we construct hermitian connections with
values in the universal differential envelope which leads us to the Schwinger
model on the sphere. The Connes-Lott program is then applied using the Hilbert
space of complexified inhomogeneous forms with its Atiyah-Kaehler structure. It
splits in two minimal left ideals of the Clifford algebra preserved by the
Dirac-Kaehler operator D=i(d-delta). The induced representation of the
universal differential envelope, in order to recover its differential
structure, is divided by the unwanted differential ideal and the obtained
quotient is the usual complexified de Rham exterior algebra over the sphere
with Clifford action on the "spinors" of the Hilbert space. The subsequent
steps of the Connes-Lott program allow to define a matter action, and the field
action is obtained using the Dixmier trace which reduces to the integral of the
curvature squared.Comment: 34 pages, Latex, submitted for publicatio
Connes-Lott model building on the two-sphere
In this work we examine generalized Connes-Lott models on the two-sphere. The
Hilbert space of the continuum spectral triple is taken as the space of
sections of a twisted spinor bundle, allowing for nontrivial topological
structure (magnetic monopoles). The finitely generated projective module over
the full algebra is also taken as topologically non-trivial, which is possible
over . We also construct a real spectral triple enlarging this Hilbert
space to include "particle" and "anti-particle" fields.Comment: 57 pages, LATE
Lorentz-violating effects in the Bose-Einstein condensation of an ideal bosonic gas
We have studied the effects of Lorentz-violation in the Bose-Einstein
condensation (BEC) of an ideal boson gas, by assessing both the nonrelativistic
and ultrarelativistic limits. Our model describes a massive complex scalar
field coupled to a CPT-even and Lorentz-violating background. We irst analyze
the nonrelativistic case, at this level by using experimental data, we obtain
upper-bounds for some LIV parameters. In the sequel, we have constructed the
partition function for the relativistic ideal boson gas which to be able of a
consistent description requires the imposition of severe restrictions on some
LIV coefficients. In both cases, we have demonstrated that the LIV
contributions are contained in an overall factor, which multiplies almost all
thermodynamical properties. An exception is the fraction of the condensed
particles.Comment: 7 pages Latex2e. To be published in Modern Physics Letters
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