327 research outputs found
Resonant nucleation of spatio-temporal order via parametric modal amplification
We investigate, analytically and numerically, the emergence of
spatio-temporal order in nonequilibrium scalar field theories. The onset of
order is triggered by destabilizing interactions (DIs), which instantaneously
change the interacting potential from a single to a double-well, tunable to be
either degenerate (SDW) or nondegenerate (ADW). For the SDW case, we observe
the emergence of spatio-temporal coherent structures known as oscillons. We
show that this emergence is initially synchronized, the result of parametric
amplification of the relevant oscillon modes. We also discuss how these ordered
structures act as bottlenecks for equipartition. For ADW potentials, we show
how the same parametric amplification mechanism may trigger the rapid decay of
a metastable state. For a range of temperatures, the decay rates associated
with this resonant nucleation can be orders of magnitude larger than those
computed by homogeneous nucleation, with time-scales given by a simple power
law, , where depends weakly on the
temperature and is the free-energy barrier of a critical
fluctuation.Comment: 38 pages, 20 figures now included within the tex
Correntropy: Implications of nonGaussianity for the moment expansion and deconvolution
Accepted versio
The 21 cm Signature of Cosmic String Wakes
We discuss the signature of a cosmic string wake in 21cm redshift surveys.
Since 21cm surveys probe higher redshifts than optical large-scale structure
surveys, the signatures of cosmic strings are more manifest in 21cm maps than
they are in optical galaxy surveys. We find that, provided the tension of the
cosmic string exceeds a critical value (which depends on both the redshift when
the string wake is created and the redshift of observation), a cosmic string
wake will generate an emission signal with a brightness temperature which
approaches a limiting value which at a redshift of is close to 400
mK in the limit of large string tension. The signal will have a specific
signature in position space: the excess 21cm radiation will be confined to a
wedge-shaped region whose tip corresponds to the position of the string, whose
planar dimensions are set by the planar dimensions of the string wake, and
whose thickness (in redshift direction) depends on the string tension. For
wakes created at , then at a redshift of the
critical value of the string tension is , and
it decreases linearly with redshift (for wakes created at the time of equal
matter and radiation, the critical value is a factor of two lower at the same
redshift). For smaller tensions, cosmic strings lead to an observable
absorption signal with the same wedge geometry.Comment: 11 pages, 4 figures; a couple of comments added in the discussion
sectio
Thermal inflation, baryogenesis and axions
In a previous paper, we proposed a simple extension of the Minimal
Supersymmetric Standard Model which gives rise to thermal inflation and
baryogenesis in a natural and remarkably consistent way. In this paper, we
consider the special case of our model, which is the minimal
way to incorporate a Peccei-Quinn symmetry. The axino/flatino becomes the
lightest supersymmetric particle with m_\axino \sim 1 to 10 \GeV and is
typically over-produced during the flaton decay. Interestingly though, the dark
matter abundance is minimized for m_\axino \sim 1 \GeV, to
10^{12} \GeV and |\mu| \sim 400 \GeV to 2 \TeV at an abundance coincident
with the observed abundance and with significant amounts of both axions and
axinos. Futhermore, for these values the baryon abundance naturally matches the
observed abundance.Comment: 53 pages, 20 figures. Figures reformatted, minor changes in Section
3, references adde
Electric current circuits in astrophysics
Cosmic magnetic structures have in common that they are anchored
in a dynamo, that an external driver converts kinetic energy into internal
magnetic energy, that this magnetic energy is transported as Poynting fl ux across the magnetically dominated structure, and that the magnetic energy
is released in the form of particle acceleration, heating, bulk motion,
MHD waves, and radiation. The investigation of the electric current system is
particularly illuminating as to the course of events and the physics involved.
We demonstrate this for the radio pulsar wind, the solar flare, and terrestrial
magnetic storms
Evidence for muon neutrino oscillation in an accelerator-based experiment
We present results for muon neutrino oscillation in the KEK to Kamioka (K2K)
long-baseline neutrino oscillation experiment. K2K uses an accelerator-produced
muon neutrino beam with a mean energy of 1.3 GeV directed at the
Super-Kamiokande detector. We observed the energy dependent disappearance of
muon neutrino, which we presume have oscillated to tau neutrino. The
probability that we would observe these results if there is no neutrino
oscillation is 0.0050% (4.0 sigma).Comment: 5 pages, 4 figure
Heavy Quarks and Heavy Quarkonia as Tests of Thermalization
We present here a brief summary of new results on heavy quarks and heavy
quarkonia from the PHENIX experiment as presented at the "Quark Gluon Plasma
Thermalization" Workshop in Vienna, Austria in August 2005, directly following
the International Quark Matter Conference in Hungary.Comment: 8 pages, 5 figures, Quark Gluon Plasma Thermalization Workshop
(Vienna August 2005) Proceeding
Single Electrons from Heavy Flavor Decays in p+p Collisions at sqrt(s) = 200 GeV
The invariant differential cross section for inclusive electron production in
p+p collisions at sqrt(s) = 200 GeV has been measured by the PHENIX experiment
at the Relativistic Heavy Ion Collider over the transverse momentum range $0.4
<= p_T <= 5.0 GeV/c at midrapidity (eta <= 0.35). The contribution to the
inclusive electron spectrum from semileptonic decays of hadrons carrying heavy
flavor, i.e. charm quarks or, at high p_T, bottom quarks, is determined via
three independent methods. The resulting electron spectrum from heavy flavor
decays is compared to recent leading and next-to-leading order perturbative QCD
calculations. The total cross section of charm quark-antiquark pair production
is determined as sigma_(c c^bar) = 0.92 +/- 0.15 (stat.) +- 0.54 (sys.) mb.Comment: 329 authors, 6 pages text, 3 figures. Submitted to Phys. Rev. Lett.
Plain text data tables for the points plotted in figures for this and
previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
Nuclear Modification of Electron Spectra and Implications for Heavy Quark Energy Loss in Au+Au Collisions at sqrt(s_NN)=200 GeV
The PHENIX experiment has measured mid-rapidity transverse momentum spectra
(0.4 < p_T < 5.0 GeV/c) of electrons as a function of centrality in Au+Au
collisions at sqrt(s_NN)=200 GeV. Contributions from photon conversions and
from light hadron decays, mainly Dalitz decays of pi^0 and eta mesons, were
removed. The resulting non-photonic electron spectra are primarily due to the
semi-leptonic decays of hadrons carrying heavy quarks. Nuclear modification
factors were determined by comparison to non-photonic electrons in p+p
collisions. A significant suppression of electrons at high p_T is observed in
central Au+Au collisions, indicating substantial energy loss of heavy quarks.Comment: 330 authors, 6 pages text, 3 figures. Submitted to Phys. Rev. Lett.
Plain text data tables for the points plotted in figures for this and
previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
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