1,645 research outputs found
Axion dark matter in a 3-3-1 model
FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORSlightly extending a right-handed neutrino version of the 3 - 3 - 1 model, we show that it is not only possible to solve the strong CP problem but also to give the total dark matter abundance reported by the Planck collaboration. Specifically, we consider the possibility of introducing a 3 - 3 - 1 scalar singlet to implement a gravity stable Peccei-Quinn mechanism in this model. Remarkably, for allowed regions of the parameter space, the arising axions with masses m(a) approximate to meV can both make up the total dark matter relic density through nonthermal production mechanisms and be very close to the region to be explored by the IAXO helioscope.976112FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIOR2014/19164-6Sem informaçã
Recurrence sequences over residual rings
In this work we are carried out an algebraic
study of the congruential lineal generator. The obtained results
make possible several combinatorial approaches that improve significantly the period length and their behavior
Chaotic dynamics in preheating after inflation
We study chaotic dynamics in preheating after inflation in which an inflaton
is coupled to another scalar field through an interaction
. We first estimate the size of the quasi-homogeneous
field at the beginning of reheating for large-field inflaton potentials
by evaluating the amplitude of the fluctuations on
scales larger than the Hubble radius at the end of inflation. Parametric
excitations of the field during preheating can give rise to chaos
between two dynamical scalar fields. For the quartic potential (,
) chaos actually occurs for in a
linear regime before which the backreaction of created particles becomes
important. This analysis is supported by several different criteria for the
existence of chaos. For the quadratic potential () the signature of chaos
is not found by the time at which the backreaction begins to work, similar to
the case of the quartic potential with .Comment: 12 pages, 10 figures, Version to appear in Classical and Quantum
Gravit
Spin-1/2 "bosons" with mass dimension 3/2 and fermions with mass dimension 1 cannot represent physical particle states
We delve into the first principles of quantum field theory to prove that the so-called spin-1/2 "bosons" and the fermions with mass dimension 1, including ELKO, cannot represent physical particle states with spin 1/2. Specifically, we first demonstrate that both aforementioned fields are not invariant under rotational symmetry, which implies that the particles created for these fields are not eigenstates of the spin operator in the (1/2, 0) circle plus (0, 1/2) representation of the Lorentz group, nor is it possible to construct a Hamiltonian density scalar under the rotational group from them. Furthermore, following Weinberg's approach to local causal fields, we prove that regardless of any discrete symmetry or adjoint structure, the relativistic fields in the (1/2, 0) circle plus (0, 1/2) representation satisfy the Fermi-Dirac statistics in complete agreement with the well-established spin-statistics theorem and experimental results.Peer reviewe
On the isospin dependence of the mean spin-orbit field in nuclei
By the use of the latest experimental data on the spectra of Sb and
Sn and on the analysis of properties of other odd nuclei adjacent to
doubly magic closed shells the isospin dependence of a mean spin-orbit
potential is defined. Such a dependence received the explanation in the
framework of different theoretical approaches.Comment: 52 pages, Revtex, no figure
Quantum corrections to the inflaton potential and the power spectra from superhorizon modes and trace anomalies
We obtain the effective inflaton potential during slow roll inflation by
including the one loop quantum corrections to the energy momentum tensor from
scalar curvature and tensor perturbations as well as quantum fluctuations from
light scalars and light Dirac fermions generically coupled to the inflaton.
During slow roll inflation there is a clean and unambiguous separation between
superhorizon and subhorizon contributions to the energy momentum tensor. The
superhorizon part is determined by the curvature perturbations and scalar field
fluctuations: both feature infrared enhancements as the inverse of a
combination of slow roll parameters which measure the departure from scale
invariance in each case.Fermions and gravitons do not exhibit infrared
divergences. The subhorizon part is completely specified by the trace anomaly
of the fields with different spins and is solely determined by the space-time
geometry. The one-loop quantum corrections to the amplitude of curvature and
tensor perturbations are obtained to leading order in slow-roll and in the
(H/M_PL)^2 expansion. This study provides a complete assessment of the
backreaction problem up to one loop including bosonic and fermionic degrees of
freedom. The result validates the effective field theory description of
inflation and confirms the robustness of the inflationary paradigm to quantum
fluctuations. Quantum corrections to the power spectra are expressed in terms
of the CMB observables:n_s, r and dn_s/dln k. Trace anomalies (especially the
graviton part) dominate these quantum corrections in a definite direction: they
enhance the scalar curvature fluctuations and reduce the tensor fluctuations.Comment: 18 pages, no figure
Strings Near a Rindler Or Black Hole Horizon
Orbifold techniques are used to study bosonic, type II and heterotic strings
in Rindler space at integer multiples N of the Rindler temperature, and near a
black hole horizon at integer multiples of the Hawking temperature, extending
earlier results of Dabholkar. It is argued that a Hagedorn transition occurs
nears the horizon for all N>1.Comment: 13 pages, harvmac, (references added
Plane waves with weak singularities
We study a class of time dependent solutions of the vacuum Einstein equations
which are plane waves with weak null singularities. This singularity is weak in
the sense that though the tidal forces diverge at the singularity, the rate of
divergence is such that the distortion suffered by a freely falling observer
remains finite. Among such weak singular plane waves there is a sub-class which
do not exhibit large back reaction in the presence of test scalar probes.
String propagation in these backgrounds is smooth and there is a natural way to
continue the metric beyond the singularity. This continued metric admits string
propagation without the string becoming infinitely excited. We construct a one
parameter family of smooth metrics which are at a finite distance in the space
of metrics from the extended metric and a well defined operator in the string
sigma model which resolves the singularity.Comment: 22 pages, Added references and clarifying comment
Comparative evaluation of therapeutic DNA vaccines against Trypanosoma cruzi in mice
Chagas disease, caused by the protozoan parasite Trypanosoma cruzi, is a major public health problem in most of Latin America. A key priority is the development of new treatments, due to the poor efficacy of current ones. We report here the comparative evaluation of therapeutic DNA vaccines encoding various T. cruzi antigens. ICR mice infected with 500 parasites intraperitoneally were treated at 5 and 12 days postinfection with 20 mu g of plasmid DNA encoding T. cruzi antigens TSA-1, TS, ASP-2-like, Tc52 or Tc24. Treatment with plasmid encoding TS and/or ASP-2-like antigens had no significant effect on parasitemia or survival. Treatment with Tc52 DNA significantly reduced parasitemia, as well as cardiac parasite burden, and improved survival, although myocarditis was not significantly affected. Finally, treatment with plasmids encoding Tc24 and TSA-1 induced the most complete control of disease as evidenced by significant reductions in parasitemia, mortality, myocarditis and heart parasite burden. These data demonstrate that therapeutic vaccine efficacy is dependent on the antigen and suggest that DNA vaccines encoding Tc24, TSA-1, and Tc52 represent the best candidates for further studies of a therapeutic vaccine against Chagas disease.Univ Autonoma Yucatan, Parasitol Lab, Ctr Invest Reg Dr Hideyo Noguchi, Merida, Yucatan, MexicoINSERM, IRD, UR 008, Ctr IRD Montpellier, Montpellier, FranceUniversidade Federal de São Paulo, CINTERGEN, Dept Microbiol Inmunol & Parasitol, São Paulo, BrazilUniversidade Federal de São Paulo, CINTERGEN, Dept Microbiol Inmunol & Parasitol, São Paulo, BrazilWeb of Scienc
CMB quadrupole suppression: II. The early fast roll stage
Within the effective field theory of inflation, an initialization of the
classical dynamics of the inflaton with approximate equipartition between the
kinetic and potential energy of the inflaton leads to a brief fast roll stage
that precedes the slow roll regime. The fast roll stage leads to an attractive
potential in the wave equations for the mode functions of curvature and tensor
perturbations. The evolution of the inflationary perturbations is equivalent to
the scattering by this potential and a useful dictionary between the scattering
data and observables is established.Implementing methods from scattering theory
we prove that this attractive potential leads to a suppression of the
quadrupole moment for CMB and B-mode angular power spectra. The scale of the
potential is determined by the Hubble parameter during slow roll. Within the
effective field theory of inflation at the grand unification (GUT) energy scale
we find that if inflation lasts a total number of efolds N_{tot} ~ 59, there is
a 10-20% suppression of the CMB quadrupole and about 2-4% suppression of the
tensor quadrupole. The suppression of higher multipoles is smaller, falling off
as 1/l^2. The suppression is much smaller for N_{tot} > 59, therefore if the
observable suppression originates in the fast roll stage, there is the upper
bound N_{tot} ~ 59.Comment: Some comments and references adde
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