17 research outputs found
Constraining the primordial spectrum of metric perturbations from gravitino and moduli production
We consider the production of gravitinos and moduli fields from quantum
vacuum fluctuations induced by the presence of scalar metric perturbations at
the end of inflation. We obtain the corresponding occupation numbers, up to
first order in perturbation theory, in terms of the power spectrum of the
metric perturbations. We compute the limits imposed by nucleosynthesis on the
spectral index for different models with constant . The results show
that, in certain cases, such limits can be as strong as , which is
more stringent than those coming from primordial black hole production.Comment: 16 pages, LaTeX, 5 figures. Corrected figures, new references
included. Final version to appear in Phys. Rev.
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.
Two-loop corrections to the fermionic decay rates of the Higgs boson
We calculate the dominant two-loop
electroweak corrections to the fermi\-onic decay widths of a heavy Higgs boson
in the Standard Model. Use of the Goldstone-boson equivalence theorem reduces
the problem to one involving only the physical Higgs boson and the
Goldstone bosons and of the unbroken theory. The two-loop
corrections are opposite in sign to the one-loop electroweak corrections,
exceed the one-loop corrections in magnitude for , and
increase in relative magnitude as for larger values of . We
conclude that the perturbation expansion in powers of breaks down
for . We discuss briefly the QCD and the complete
one-loop electroweak corrections to , and
comment on the validity of the equivalence theorem. Finally we note how a very
heavy Higgs boson could be described in a phenomenological manner.Comment: 24 pages, RevTeX file, 4 figures in a separate compressed uuencoded
Postscript file or available by mail on request. Fig. 1 not included see
Figs. 1, 2 in Phys. Rev. D 48, 1061 (1993
Childhood ADHD and Involvement in Early Pregnancy: Mechanisms of Risk
Objective: ADHD is associated with risky sexual behavior and early pregnancy, but few studies have examined mechanisms of risk linking childhood ADHD to early pregnancy. The present study utilized data from the Multimodal Treatment Study of ADHD to examine potential mechanisms that may account for the association between childhood ADHD and becoming pregnant or causing a pregnancy by age 18. Method: Participants were 579 children with ADHD and 289 comparison peers followed over 16 years. Results: Relative to the comparison group, those with childhood ADHD were at more than two times increased risk of early pregnancy. Univariately, persistence of ADHD symptoms, delinquency/substance use, and academic performance/achievement during adolescence each mediated the association between childhood ADHD and early pregnancy. When considered together, only delinquency/substance use remained a significant mediator of this relationship. Conclusion: Findings point toward specific targets of intervention for youth with ADHD to prevent early pregnancy