37,593 research outputs found
Symplectic gauge fields and dark matter
The dynamics of symplectic gauge fields provides a consistent framework for
fundamental interactions based on spin three gauge fields. One remarkable
property is that symplectic gauge fields only have minimal couplings with
gravitational fields and not with any other field of the Standard Model.
Interactions with ordinary matter and radiation can only arise from radiative
corrections. In spite of the gauge nature of symplectic fields they acquire a
mass by the Coleman-Weinberg mechanism which generates Higgs-like mass terms
where the gravitational field is playing the role of a Higgs field. Massive
symplectic gauge fields weakly interacting with ordinary matter are natural
candidates for the dark matter component of the Universe.Comment: 16 page
Casimir Effect and Global Theory of Boundary Conditions
The consistency of quantum field theories defined on domains with external
borders imposes very restrictive constraints on the type of boundary conditions
that the fields can satisfy. We analyse the global geometrical and topological
properties of the space of all possible boundary conditions for scalar quantum
field theories. The variation of the Casimir energy under the change of
boundary conditions reveals the existence of singularities generically
associated to boundary conditions which either involve topology changes of the
underlying physical space or edge states with unbounded below classical energy.
The effect can be understood in terms of a new type of Maslov index associated
to the non-trivial topology of the space of boundary conditions. We also
analyze the global aspects of the renormalization group flow, T-duality and the
conformal invariance of the corresponding fixed points.Comment: 11 page
High Resolution Infrared Spectroscopy Techniques for Upper Atmospheric Measurements
Infrared heterodyne techniques were considered primarily for detecting molecules predicted to be present but not yet detected in the upper atmosphere
Non-analyticities in three-dimensional gauge theories
Quantum fluctuations generate in three-dimensional gauge theories not only
radiative corrections to the Chern-Simons coupling but also non-analytic terms
in the effective action. We review the role of those terms in gauge theories
with massless fermions and Chern-Simons theories. The explicit form of
non-analytic terms turns out to be dependent on the regularization scheme and
in consequence the very existence of phenomena like parity and framing
anomalies becomes regularization dependent. In particular we find
regularization regimes where both anomalies are absent. Due to the presence of
non-analytic terms the effective action becomes not only discontinuous but also
singular for some background gauge fields which include sphalerons. The
appearence of this type of singularities is linked to the existence of nodal
configurations in physical states and tunneling suppression at some classical
field configurations. In the topological field theory the number of physical
states may also become regularization dependent. Another consequence of the
peculiar behaviour of three-dimensional theories under parity odd
regularizations is the existence of a simple mechanism of generation of a mass
gap in pure Yang-Mills theory by a suitable choice of regularization scheme.
The generic value of this mass does agree with the values obtained in
Hamiltonian and numerical analysis. Finally, the existence of different
regularization regimes unveils the difficulties of establishing a Zamolodchikov
c-theorem for three-dimensional field theories in terms of the induced
gravitational Chern-Simons couplings.Comment: 21 pages; Contribution to Ian Kogan Memorial Collection, ``From
Fields to Strings: Circumnavigating Theoretical Physics'
Period-Luminosity-Colour distribution and classification of Galactic oxygen-rich LPVs
The absolute K magnitudes and kinematic parameters of about 350 oxygen-rich
Long-Period Variable stars are calibrated, by means of an up-to-date
maximum-likelihood method, using Hipparcos parallaxes and proper motions
together with radial velocities and, as additional data, periods and V-K colour
indices. Four groups, differing by their kinematics and mean magnitudes, are
found. For each of them, we also obtain the distributions of magnitude, period
and de-reddened colour of the base population, as well as de-biased
period-luminosity-colour relations and their two-dimensional projections. The
SRa semiregulars do not seem to constitute a separate class of LPVs. The SRb
appear to belong to two populations of different ages. In a PL diagram, they
constitute two evolutionary sequences towards the Mira stage. The Miras of the
disk appear to pulsate on a lower-order mode. The slopes of their de-biased PL
and PC relations are found to be very different from the ones of the Oxygen
Miras of the LMC. This suggests that a significant number of so-called Miras of
the LMC are misclassified. This also suggests that the Miras of the LMC do not
constitute a homogeneous group, but include a significant proportion of
metal-deficient stars, suggesting a relatively smooth star formation history.
As a consequence, one may not trivially transpose the LMC period-luminosity
relation from one galaxy to the other.Comment: 13 pages, 23 figures. Accepted for publication in A&A
Decoupling of Heavy Kaluza-Klein Modes In Models With Five-Dimensional Scalar Fields
We investigate the decoupling of heavy Kaluza-Klein modes in
theory and scalar QED with space-time topology .
We calculate the effective action due to integrating out heavy KK modes. We
construct generalized RGE's for the couplings with respect to the
compactification scale . With the solutions to the RGE's we find the
-scale dependence of the effective theory due to higher dimensional quantum
effects. We find that the heavy modes decouple in theory, but do not
decouple in scalar QED. This is due to the zero mode of the 5-th component
of the 5-d gauge field. Because is a scalar under 4-d Lorentz
transformations, there is no gauge symmetry protecting it from getting mass and
interaction terms after loop corrections. In light of these
unpleasant features, we explore compactifications, which
eliminate , allowing for the heavy modes to decouple at low energies. We
also explore the possibility of decoupling by including higher dimensional
operators. It is found that this is possible, but a high degree of fine tuning
is required.Comment: 9 pages, no figures; sign error on equations 20, 36, 37; Added
additional reference
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