8,904 research outputs found
Solar mass-varying neutrino oscillations
We propose that the solar neutrino deficit may be due to oscillations of
mass-varying neutrinos (MaVaNs). This scenario elucidates solar neutrino data
beautifully while remaining comfortably compatible with atmospheric neutrino
and K2K data and with reactor antineutrino data at short and long baselines
(from CHOOZ and KamLAND). We find that the survival probability of solar MaVaNs
is independent of how the suppression of neutrino mass caused by the
acceleron-matter couplings varies with density. Measurements of MeV and lower
energy solar neutrinos will provide a rigorous test of the idea.Comment: 4 pages, 3 figures. Version to appear in PR
Enhancement of the electric dipole moment of the electron in the YbF molecule
We calculate an effective electric field on the unpaired electron in the YbF
molecule. This field determines sensitivity of the molecular experiment to the
electric dipole moment of the electron. We use experimental value of the
spin-doubling constant to estimate the admixture of the configuration with the
hole in the 4f-shell of Ytterbium to the ground state of the molecule. This
admixture reduces the field by 7%. Our value for the effictive field is 5.1
a.u. = 2.5 10^{10} V/cm.Comment: 5 pages, LATEX, uses revtex.st
Using Molecules to Measure Nuclear Spin-Dependent Parity Violation
Nuclear spin-dependent parity violation arises from weak interactions between
electrons and nucleons, and from nuclear anapole moments. We outline a method
to measure such effects, using a Stark-interference technique to determine the
mixing between opposite-parity rotational/hyperfine levels of ground-state
molecules. The technique is applicable to nuclei over a wide range of atomic
number, in diatomic species that are theoretically tractable for
interpretation. This should provide data on anapole moments of many nuclei, and
on previously unmeasured neutral weak couplings
The role of matter density uncertainties in the analysis of future neutrino factory experiments
Matter density uncertainties can affect the measurements of the neutrino
oscillation parameters at future neutrino factory experiments, such as the
measurements of the mixing parameters and \deltacp. We compare
different matter density uncertainty models and discuss the possibility to
include the matter density uncertainties in a complete statistical analysis.
Furthermore, we systematically study in which measurements and where in the
parameter space matter density uncertainties are most relevant. We illustrate
this discussion with examples that show the effects as functions of different
magnitudes of the matter density uncertainties. We find that matter density
uncertainties are especially relevant for large \stheta \gtrsim 10^{-3}.
Within the KamLAND-allowed range, they are most relevant for the precision
measurements of \stheta and \deltacp, but less relevant for ``binary''
measurements, such as for the sign of \ldm, the sensitivity to \stheta, or
the sensitivity to maximal CP violation. In addition, we demonstrate that
knowing the matter density along a specific baseline better than to about 1%
precision means that all measurements will become almost independent of the
matter density uncertainties.Comment: 21 pages, 7 figures, LaTeX. Final version to be published in Phys.
Rev.
Production of Gravitational Waves in the nMSSM
During a strongly first-order phase transition gravitational waves are
produced by bubble collisions and turbulent plasma motion. We analyze the
relevant characteristics of the electroweak phase transition in the nMSSM to
determine the generated gravitational wave signal. Additionally, we comment on
correlations between the production of gravitational waves and baryogenesis. We
conclude that the gravitational wave relic density in this model is generically
too small to be detected in the near future by the LISA experiment. We also
consider the case of a "Standard Model" with dimension-six Higgs potential,
which leads to a slightly stronger signal of gravitational waves.Comment: 29 pages, 7 figures; published version, some comments adde
Hierarchical versus degenerate 2HDM: the LHC run 1 legacy at the onset of run 2
Current discussions of the allowed two-Higgs-doublet model parameter space after LHC run 1 and the prospects for run 2 are commonly phrased in the context of a quasidegenerate spectrum for the new scalars. Here, we discuss the generic situation of a two-Higgs-doublet model with a nondegenerate spectrum for the new scalars. This is highly motivated from a cosmological perspective since it naturally leads to a strongly first-order electroweak phase transition that could explain the matter-antimatter asymmetry in the Universe. While constraints from measurements of Higgs signal strengths do not change, those from searches of new scalar states get modified dramatically once a nondegenerate spectrum is considered
Faraday Instability in a Surface-Frozen Liquid
Faraday surface instability measurements of the critical acceleration, a_c,
and wavenumber, k_c, for standing surface waves on a tetracosanol (C_24H_50)
melt exhibit abrupt changes at T_s=54degC above the bulk freezing temperature.
The measured variations of a_c and k_c vs. temperature and driving frequency
are accounted for quantitatively by a hydrodynamic model, revealing a change
from a free-slip surface flow, generic for a free liquid surface (T>T_s), to a
surface-pinned, no-slip flow, characteristic of a flow near a wetted solid wall
(T < T_s). The change at T_s is traced to the onset of surface freezing, where
the steep velocity gradient in the surface-pinned flow significantly increases
the viscous dissipation near the surface.Comment: 4 pages, 3 figures. Physical Review Letters (in press
Injective split systems
A split system on a finite set , , is a set of
bipartitions or splits of which contains all splits of the form
, . To any such split system we can
associate the Buneman graph which is essentially a
median graph with leaf-set that displays the splits in . In
this paper, we consider properties of injective split systems, that is, split
systems with the property that for any 3-subsets
in , where denotes the median in
of the three elements in considered as leaves in
. In particular, we show that for any set there
always exists an injective split system on , and we also give a
characterization for when a split system is injective. We also consider how
complex the Buneman graph needs to become in order for
a split system on to be injective. We do this by introducing a
quantity for which we call the injective dimension for , as well as
two related quantities, called the injective 2-split and the rooted-injective
dimension. We derive some upper and lower bounds for all three of these
dimensions and also prove that some of these bounds are tight. An underlying
motivation for studying injective split systems is that they can be used to
obtain a natural generalization of symbolic tree maps. An important consequence
of our results is that any three-way symbolic map on can be represented
using Buneman graphs.Comment: 22 pages, 3 figure
Critical behavior of the (2+1)-dimensional Thirring model
We investigate chiral symmetry breaking in the (2+1)-dimensional Thirring
model as a function of the coupling as well as the Dirac flavor number Nf with
the aid of the functional renormalization group. For small enough flavor number
Nf < Nfc, the model exhibits a chiral quantum phase transition for sufficiently
large coupling. We compute the critical exponents of this second order
transition as well as the fermionic and bosonic mass spectrum inside the broken
phase within a next-to-leading order derivative expansion. We also determine
the quantum critical behavior of the many-flavor transition which arises due to
a competition between vector and chiral-scalar channel and which is of second
order as well. Due to the problem of competing channels, our results rely
crucially on the RG technique of dynamical bosonization. For the critical
flavor number, we find Nfc ~ 5.1 with an estimated systematic error of
approximately one flavor.Comment: 28 pages, 14 figure
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