3,422 research outputs found
Strange Quarks Nuggets in Space: Charges in Seven Settings
We have computed the charge that develops on an SQN in space as a result of
balance between the rates of ionization by ambient gammas and capture of
ambient electrons. We have also computed the times for achieving that
equilibrium and binding energy of the least bound SQN electrons. We have done
this for seven different settings. We sketch the calculations here and give
their results in the Figure and Table II; details are in the Physical Review
D.79.023513 (2009).Comment: Six pages, one figure. To appear in proceedings of the 2008 UCLA
coference on dark matter and dark energ
Protecting the Primordial Baryon Asymmetry From Erasure by Sphalerons
If the baryon asymmetry of the universe was created at the GUT scale,
sphalerons together with exotic sources of -violation could have erased
it, unless the latter satisfy stringent bounds. We elaborate on how the small
Yukawa coupling of the electron drastically weakens previous estimates of these
bounds.Comment: 41 pp., 4 latex figures included and 3 uuencoded or postscript
figures available by request, UMN-TH-1213-9
Relic gravitational waves and present accelerated expansion
We calculate the current power spectrum of the gravitational waves created at
the big bang (and later amplified by the different transitions during the
Universe expansion) taking into account the present stage of accelerated
expansion. Likewise, we determine the power spectrum in a hypothetical second
dust era that would follow the present one if at some future time the dark
energy, that supposedly drives the current accelerated expansion, evolved in
such a way that it became dynamically equivalent to cold dark matter. The
calculated power spectrum as well as the evolution of the density parameter of
the waves may serve to discriminate between phases of expansion and may help
ascertain the nature of dark energy.Comment: 20 pages, uses revtex4, 1 figure ps and 3 figures eps. To be
published in Physical Review
Primordial magnetic fields, anomalous isocurvature fluctuations and Big Bang nucleosynthesis
We show that the presence of primordial stochastic (hypercharge) magnetic
fields before the electroweak (EW) phase transition induces isocurvature
fluctuations (baryon number inhomogeneities). Depending on the details of the
magnetic field spectrum and on the particle physics parameters (such as the
strength of the EW phase transition and electron Yukawa couplings) these
fluctuations may survive until the Big Bang nucleosynthesis (BBN). Their
lenghtscale may exceed the neutron diffusion length at that time, while their
magnitude can be so large that sizable antimatter domains are present. This
provides the possibility of a new type of initial conditions for
non-homogeneous BBN or, from a more conservative point of view, stringent
bounds on primordial magnetic fields.Comment: 4 pages, Latex, 1 epsfi
Observations of giant outbursts from Cygnus X-1
We present interplanetary network localization, spectral, and time history
information for 7 episodes of exceptionally intense gamma-ray emission from
Cygnus X-1. The outbursts occurred between 1995 and 2003, with durations up to
\~28000 seconds. The observed 15 - 300 keV peak fluxes and fluences reached
3E-7 erg /cm2 s, and 8E-4 erg / cm2 respectively. By combining the
triangulations of these outbursts we derive an ~1700 square arcminute (3 sigma)
error ellipse which contains Cygnus X-1 and no other known high energy sources.
The outbursts reported here occurred both when Cyg X-1 was in the hard state as
well as in the soft one, and at various orbital phases. The spectral data
indicate that these outbursts display the same parameters as those of the
underlying hard and soft states, suggesting that they represent another
manifestation of these states.Comment: 27 pages, 9 figures. Revised version. Accepted for publication in the
Astrophysical Journal, tentatively scheduled for October 20, 2003 Part
Primordial Magnetic Fields, Right Electrons, and the Abelian Anomaly
In the standard model there are charges with abelian anomaly only (e.g.
right-handed electron number) which are effectively conserved in the early
universe until some time shortly before the electroweak scale. A state at
finite chemical potential of such a charge, possibly arising due to asymmetries
produced at the GUT scale, is unstable to the generation of hypercharge
magnetic field. Quite large magnetic fields ( gauss at GeV with typical inhomogeneity scale ) can be
generated. These fields may be of cosmological interest, potentially acting as
seeds for amplification to larger scale magnetic fields through non-linear
mechanisms. Previously derived bounds on exotic violating operators may
also be evaded.Comment: Revised version, to appear in Phys. Rev. Lett.. Analysis has been
extended to larger chemical potentials, for which large magnetic fields
survive at the electroweak scale. Previous bounds on violating
operators are also evaded in this cas
Primordial Hypermagnetic Knots
Topologically non-trivial configurations of the hypermagnetic flux lines lead
to the formation of hypermagnetic knots (HK) whose decay might seed the Baryon
Asymmetry of the Universe (BAU).HK can be dynamically generated provided a
topologically trivial (i.e. stochastic) distribution of flux lines is already
present in the symmetric phase of the electroweak (EW) theory. In spite of the
mechanism generating the HK, their typical size must exceed the diffusivity
length scale. In the minimal standard model (MSM) (but not necessarily in its
supersymmetric extension) HK are washed out. A classical hypermagnetic
background in the symmetric phase of the EW theory can produce interesting
amounts of gravitational radiation.Comment: 4 pages in Revtex style, 2 figure
New Test of Supernova Electron Neutrino Emission using Sudbury Neutrino Observatory Sensitivity to the Diffuse Supernova Neutrino Background
Supernovae are rare nearby, but they are not rare in the Universe, and all
past core-collapse supernovae contributed to the Diffuse Supernova Neutrino
Background (DSNB), for which the near-term detection prospects are very good.
The Super-Kamiokande limit on the DSNB electron {\it antineutrino} flux,
cm s, is just above the
range of recent theoretical predictions based on the measured star formation
rate history. We show that the Sudbury Neutrino Observatory should be able to
test the corresponding DSNB electron {\it neutrino} flux with a sensitivity as
low as cm s,
improving the existing Mont Blanc limit by about three orders of magnitude.
While conventional supernova models predict comparable electron neutrino and
antineutrino fluxes, it is often considered that the first (and
forward-directed) SN 1987A event in the Kamiokande-II detector should be
attributed to electron-neutrino scattering with an electron, which would
require a substantially enhanced electron neutrino flux. We show that with the
required enhancements in either the burst or thermal phase fluxes, the
DSNB electron neutrino flux would generally be detectable in the Sudbury
Neutrino Observatory. A direct experimental test could then resolve one of the
enduring mysteries of SN 1987A: whether the first Kamiokande-II event reveals a
serious misunderstanding of supernova physics, or was simply an unlikely
statistical fluctuation. Thus the electron neutrino sensitivity of the Sudbury
Neutrino Observatory is an important complement to the electron antineutrino
sensitivity of Super-Kamiokande in the quest to understand the DSNB.Comment: 10 pages, 3 figure
New Solutions of the Inflationary Flow Equations
The inflationary flow equations are a frequently used method of surveying the
space of inflationary models. In these applications the infinite hierarchy of
differential equations is truncated in a way which has been shown to be
equivalent to restricting the set of models considered to those characterized
by polynomial inflaton potentials. This paper explores a different method of
solving the flow equations, which does not truncate the hierarchy and in
consequence covers a much wider class of models while retaining the practical
usability of the standard approach.Comment: References added, and a couple of comment
The Light Stop Scenario from Gauge Mediation
In this paper we embed the light stop scenario, a MSSM framework which
explains the baryon asymmetry of the universe through a strong first order
electroweak phase transition, in a top-down approach. The required low energy
spectrum consists in the light SM-like Higgs, the right-handed stop, the
gauginos and the Higgsinos while the remaining scalars are heavy. This spectrum
is naturally driven by renormalization group evolution starting from a heavy
scalar spectrum at high energies. The latter is obtained through a
supersymmetry-breaking mix of gauge mediation, which provides the scalars
masses by new gauge interactions, and gravity mediation, which generates
gaugino and Higgsino masses. This supersymmetry breaking also explains the \mu\
and B_\mu\ parameters necessary for electroweak breaking and predicts small
tri-linear mixing terms A_t in agreement with electroweak baryogenesis
requirements. The minimal embedding predicts a Higgs mass around its
experimental lower bound and by a small extension higher masses m_H\lesssim 127
GeV can be accommodated.Comment: 20 pages, 3 figures; v2: changes in the conventions; v3: more details
on the Higgs mass prediction, version published in JHE
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