56 research outputs found
Density perturbations in generalized Einstein scenarios and constraints on nonminimal couplings from the Cosmic Microwave Background
We study cosmological perturbations in generalized Einstein scenarios and
show the equivalence of inflationary observables both in the Jordan frame and
the Einstein frame. In particular the consistency relation relating the
tensor-to-scalar ratio with the spectral index of tensor perturbations
coincides with the one in Einstein gravity, which leads to the same likelihood
results in terms of inflationary observables. We apply this formalism to
nonminimally coupled chaotic inflationary scenarios with potential
and place constraints on the strength of nonminimal couplings using a
compilation of latest observational data. In the case of the quadratic
potential (), the nonminimal coupling is constrained to be for negative from the observational contour
bound. Although the quartic potential () is under a strong observational
pressure for , this property is relaxed by taking into account negative
nonminimal couplings. We find that inflationary observables are within the
contour bound as long as . We also show that
the cases are disfavoured even in the presence of nonminimal
couplings.Comment: 16 pages, 4 eps figure
Large-scale magnetic fields from inflation due to a -even Chern-Simons-like term with Kalb-Ramond and scalar fields
We investigate the generation of large-scale magnetic fields due to the
breaking of the conformal invariance in the electromagnetic field through the
-even dimension-six Chern-Simons-like effective interaction with a fermion
current by taking account of the dynamical Kalb-Ramond and scalar fields in
inflationary cosmology. It is explicitly demonstrated that the magnetic fields
on 1Mpc scale with the field strength of G at the present time
can be induced.Comment: 18 pages, 6 figures, version accepted for publication in Eur. Phys.
J.
Modern temporal network theory: A colloquium
The power of any kind of network approach lies in the ability to simplify a
complex system so that one can better understand its function as a whole.
Sometimes it is beneficial, however, to include more information than in a
simple graph of only nodes and links. Adding information about times of
interactions can make predictions and mechanistic understanding more accurate.
The drawback, however, is that there are not so many methods available, partly
because temporal networks is a relatively young field, partly because it more
difficult to develop such methods compared to for static networks. In this
colloquium, we review the methods to analyze and model temporal networks and
processes taking place on them, focusing mainly on the last three years. This
includes the spreading of infectious disease, opinions, rumors, in social
networks; information packets in computer networks; various types of signaling
in biology, and more. We also discuss future directions.Comment: Final accepted versio
Electromagnetic and electric field configurations produced by two coils.
Journal ArticleSCOPUS: ar.jinfo:eu-repo/semantics/publishe
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