7,608 research outputs found
The 125 GeV boson: A composite scalar?
Assuming that the 125 GeV particle observed at the LHC is a composite scalar
and responsible for the electroweak gauge symmetry breaking, we consider the
possibility that the bound state is generated by a non-Abelian gauge theory
with dynamically generated gauge boson masses and a specific chiral symmetry
breaking dynamics motivated by confinement. The scalar mass is computed with
the use of the Bethe-Salpeter equation and its normalization condition as a
function of the SU(N) group and the respective fermionic representation. If the
fermions that form the composite state are in the fundamental representation of
the SU(N) group, we can generate such light boson only for one specific number
of fermions for each group. In the case of small groups, like SU(2) to SU(5),
and two fermions in the adjoint representation we find that is quite improbable
to generate such light composite scalar.Comment: 24 pages, 5 figures, discussion extended, references added; version
to appear in Phys. Rev.
Spectral Characters of Finite-Dimensional Representations of Affine Algebras
We introduce the notion of a spectral character for finite-dimensional
representations of affine algebras. These can be viewed as a suitable q=1 limit
of the elliptic characters defined by Etingof and Moura for quantum affine
algebras. We show that these characters determine blocks of the category of
finite-dimensional modules for affine algebras. To do this we use the Weyl
modules defined by Chari and Pressley and some indecomposable reducible
quotient of the Weyl modules.Comment: More concise proofs for Propositions 1.2 and 2.4 added. To appear in
Journal of Algebr
Gain and noise spectral density in an electronic parametric amplifier with added white noise
In this paper, we discuss the behavior of a linear classical parametric
amplifier (PA) in the presence of white noise and give theoretical estimates of
the noise spectral density based on approximate Green's functions obtained by
using averaging techniques. Furthermore, we give analytical estimates for
parametric amplification bandwidth of the amplifier and for the noisy
precursors to instability. To validate our theory we compare the analytical
results with experimental data obtained in an analog circuit. We describe the
implementation details and the setup used in the experimental study of the
amplifier. Near the threshold to the first parametric instability, and in
degenerate-mode amplification, the PA achieved very high gains in a very narrow
bandwidth centered on its resonance frequency. In quasi-degenerate mode
amplification, we obtained lower values of gain, but with a wider bandwidth
that is tunable. The experimental data were accurately described by the
predictions of the model. Moreover, we noticed spectral components in the
output signal of the amplifier which are due to noise precursors of
instability. The position, width, and magnitude of these components are in
agreement with the noise spectral density obtained by the theory proposed here
Three-antenna two-dimensional imaging correlation radiometer: concept and preliminary results
Peer ReviewedPostprint (published version
Inflation in asymptotically safe f(R) theory
We discuss the existence of inflationary solutions in a class of
renormalization group improved polynomial f(R) theories, which have been
studied recently in the context of the asymptotic safety scenario for quantum
gravity. These theories seem to possess a nontrivial ultraviolet fixed point,
where the dimensionful couplings scale according to their canonical
dimensionality. Assuming that the cutoff is proportional to the Hubble
parameter, we obtain modified Friedmann equations which admit both power law
and exponential solutions. We establish that for sufficiently high order
polynomial the solutions are reliable, in the sense that considering still
higher order polynomials is very unlikely to change the solution.Comment: Presented at 14th Conference on Recent Developments in Gravity: NEB
14, Ioannina, Greece, 8-11 Jun 201
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