34 research outputs found
Inferring type and scale of noncommutativity from the PTOLEMY experiment
If neutrinos are Dirac particles and their right-handed component can be
copiously produced in the early universe, then they could influence a direct
observation of the cosmic neutrino background, which, most likely, will come
about with the recently proposed PTOLEMY experiment. For the production
mechanism of right-handed neutrinos we use a state-of-the-art version of gauge
field theory deformed by the spacetime noncommutativity, to disclose by it not
only the decoupling temperature for the said neutrino component, but also the
otherwise hidden coupling temperature. Considering two relevant processes, the
plasmon decay and the neutrino elastic scattering, we study the interplay
between the structure of the noncommutativity parameter
(type of noncommutativity) and the reheating temperature after inflation to
obtain otherwise elusive upper bound on the scale of noncommutativity
. If PTOLEMY enhanced capture rate is due to spacetime
noncommutativity, we verify that a nontrivial maximum upper bound on
(a way below the Planck scale) emerges for a space-like
and sufficiently high reheating temperature.Comment: 6 pagees, 1 figure, version of article to be published in EPJ
Momentum-independent renormalization of the Schwinger-Dyson equation with an instantaneous-interaction kernel
We consider the problem of renormalization of the Schwinger-Dyson equation, encountered when the interquark interaction kernel is modeled by an instantaneous potential. More precisely, the Coulomb potential, needed for describing the short-distance part of the gluon exchange, leads to ultraviolet divergences in the Schwinger-Dyson equation. The standard prescription which has been used up till now to subtract these divergences, suffers from a serious conceptual problem: it is not momentum independent. In this work we propose a new and momentum-independent renormalization prescription, and take special care to preserve the correct chiral limit for light pseudoscalar mesons
Impulsno neovisna renormalizacija Schwinger–Dysonove jednadžbe s trenutnom interakcijom
We consider the problem of renormalization of the Schwinger-Dyson equation, encountered when the interquark interaction kernel is modeled by an instantaneous potential. More precisely, the Coulomb potential, needed for describing the short-distance part of the gluon exchange, leads to ultraviolet divergences in the Schwinger-Dyson equation. The standard prescription which has been used up till now to subtract these divergences, suffers from a serious conceptual problem: it is not momentum independent. In this work we propose a new and momentum-independent renormalization prescription, and take special care to preserve the correct chiral limit for light pseudoscalar mesons.Razmatramo problem koji se prilikom renormalizacije Schwinger–Dysonove jednadžbe susreće kada je jezgra medukvarkovske interakcije modelirana trenutnim potencijalom. Preciznije, Coulombov potencijal, potreban za opis gluonske izmjene na malim udaljenostima izmedu kvarkova, dovodi do ultraljubičastih divergencija u Schwinger–Dysonovoj jednadžbi. Standardna postavka koja se dosad upotrebljavala za uklanjanje tih divergencija ima ozbiljan konceptualan problem: ona nije impulsno neovisna. U ovom radu predlažemo jednu novu impulsno neovisnu postavku, pri čemu posebno pazimo da bude očuvan ispravan kiralni limes za lagane pseudoskalarne mezone
Constraining interacting dark energy models with flux destabilization
A destabilization in the transfer energy flux from the vacuum to radiation,
for two vacuum decay laws relevant to the dark energy problem, is analyzed
using the Landau-Lifshitz fluctuation hydrodynamic theory. Assuming thermal (or
near thermal) equilibrium between the vacuum and radiation, at the earliest
epoch of the Universe expansion, we show that the law due to
renormalization-group running of the cosmological constant term, with
parameters chosen not to spoil the primordial nucleosynthesis scenario, does
soon drive the flux to fluctuate beyond its statistical average value thereby
distorting the cosmic background radiation spectrum beyond observational
limits. While the law coming from the saturated holographic dark energy does
not lead the flux to wildly fluctuate, a more realistic non--saturated form
shows again such anomalous behavior.Comment: 12 pages, minor correction, to appear in Physics Letters