114 research outputs found
Antecedent generics: how capes, lakes, mounts, and points are named in the Antipodes
Toponymic literature often mentions that the names of geographic features generally have the structure: specific + generic. While this is often the case, there are a set of geographic features that regularly do not follow this sequence. These are capes, lakes, mountains, and points. Their order of elements is often the reverse: generic + specific. By using toponyms from the Gazetteer of Australia and the New Zealand Gazetteer, this article shows there is indeed a distinct and suggestive pattern to the names that these features bear, explores this phenomenon and attempts to discover reasons for this trend
Simulations of Cold Electroweak Baryogenesis
We present real-time lattice simulations of Cold Electroweak Baryogenesis, in
which the baryon asymmetry of the Universe is generated during tachyonic
electroweak symmetry breaking at the end of inflation. In the minimal
realisation of the model, only three parameters remain undetermined: the
strength of CP-violation, the Higgs mass and the speed of the symmetry breaking
quench. The dependence of the asymmetry on these parameters is studied.Comment: 4 pages. Presented at International Conference on Strong and
Electroweak Matter (SEWM 2006), Upton, New York, 10-13 May 200
Simulations of Cold Electroweak Baryogenesis: Finite time quenches
The electroweak symmetry breaking transition may supply the appropriate
out-of-equilibrium conditions for baryogenesis if it is triggered sufficiently
fast. This can happen at the end of low-scale inflation, prompting baryogenesis
to occur during tachyonic preheating of the Universe, when the potential energy
of the inflaton is transfered into Standard Model particles. With the proper
amount of CP-violation present, the observed baryon number asymmetry can be
reproduced. Within this framework of Cold Electroweak Baryogenesis, we study
the dependence of the generated baryon asymmetry on the speed of the quenching
transition. We find that there is a separation between ``fast'' and ``slow''
quenches, which can be used to put bounds on the allowed Higgs-inflaton
coupling. We also clarify the strong Higgs mass dependence of the asymmetry
reported in a companion paper (hep-ph/0604263).Comment: 18 pages, 20 figure
Effective CP violation in the Standard Model
We study the strength of effective CP violation originating from the CKM
matrix in the effective action obtained by integrating out the fermions in the
Standard Model. Using results obtained by Salcedo for the effective action in a
general chiral gauge model, we find that there are no CKM CP-violating terms to
fourth order in a gauge-covariant derivative expansion that is non-perturbative
in the Higgs field. The details of the calculation suggest that, at zero
temperature, the strength of CP violation is approximately independent of the
overall scale of the Yukawa couplings. Thus, order of magnitude estimates based
on Jarlskog's invariant could be too small by a factor of about 10^{17}.Comment: 19 pages, no figure
Tachyonic preheating using 2PI-1/N dynamics and the classical approximation
We study the process of tachyonic preheating using approximative quantum
equations of motion derived from the 2PI effective action. The O(N) scalar
(Higgs) field is assumed to experience a fast quench which is represented by an
instantaneous flip of the sign of the mass parameter. The equations of motion
are solved numerically on the lattice, and the Hartree and 1/N-NLO
approximations are compared to the classical approximation. Classical dynamics
is expected to be valid, since the occupation numbers can rise to large values
during tachyonic preheating. We find that the classical approximation performs
excellently at short and intermediate times, even for couplings in the larger
region currently allowed for the SM Higgs. This is reassuring, since all
previous numerical studies of tachyonic preheating and baryogenesis during
tachyonic preheating have used classical dynamics. We also compare different
initializations for the classical simulations.Comment: 32 pages, 21 figures. Published version: Some details added, section
added, references added, conclusions unchange
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