1,032 research outputs found

### Spontaneous CP Symmetry Breaking at the Electroweak Scale

We present a top-condensation model in which the CP symmetry is spontaneously
broken at the electroweak scale due to the condensation of two composite Higgs
doublets. In particular the CP-violating phase of the CKM matrix is generated.
A simpler model where only one quark family is included is also discussed. In
this case, for a general four-fermion interaction ($G_{tb}\neq 0$), the
particle spectrum is the one of the one Higgs doublet model.Comment: 25 pages, LaTeX. References and comment adde

### Neutrinos in IceCube/KM3NeT as probes of Dark Matter Substructures in Galaxy Clusters

Galaxy clusters are one of the most promising candidate sites for dark matter
annihilation. We focus on dark matter with mass in the range 10 GeV - 100 TeV
annihilating to muon pairs, neutrino pairs, top pairs, or two neutrino pairs,
and forecast the expected sensitivity to the annihilation cross section into
these channels by observing galaxy clusters at IceCube/KM3NeT. Optimistically,
the presence of dark matter substructures in galaxy clusters is predicted to
enhance the signal by 2-3 orders of magnitude over the contribution from the
smooth component of the dark matter distribution. Optimizing for the angular
size of the region of interest for galaxy clusters, the sensitivity to the
annihilation cross section of heavy DM with mass in the range 300 GeV - 100 TeV
will be of the order of 10^{-24} cm^3 s^{-1}, for full IceCube/KM3NeT live time
of 10 years, which is about one order of magnitude better than the best limit
that can be obtained by observing the Milky Way halo. We find that neutrinos
from cosmic ray interactions in the galaxy cluster, in addition to the
atmospheric neutrinos, are a source of background. We show that significant
improvement in the experimental sensitivity can be achieved for lower DM masses
in the range 10 GeV - 300 GeV if neutrino-induced cascades can be reconstructed
to approximately 5 degrees accuracy, as may be possible in KM3NeT. We therefore
propose that a low-energy extension "KM3NeT-Core", similar to DeepCore in
IceCube, be considered for an extended reach at low DM masses.Comment: v2: 17 pages, 5 figures. Neutrino spectra corrected, dependence on
dark matter substructure model included, references added. Results unchanged.
Accepted in PR

### Cosmic superstring trajectories in warped compactifications

We explore the generic motion of cosmic (super)strings when the internal
compact dimensions are warped, using the Klebanov-Strassler solution as a
prototypical throat geometry. We find that there is no dynamical mechanism
which localises the string at the tip of the throat, but rather that the motion
seems to explore both internal and external degrees of freedom democratically.
This indicates that cosmic (super)strings formed by inflationary
brane-antibrane annihilation will have sufficient internal motion for the
gravitational wave signals from the string network to be suppressed relative to
the signal from a `standard' cosmic string network.Comment: 31 pages, 8 figure

### Sequestering the standard model vacuum energy

We propose a very simple reformulation of general relativity, which completely sequesters from gravity all of the vacuum energy from a matter sector, including all loop corrections and renders all contributions from phase transitions automatically small. The idea is to make the dimensional parameters in the matter sector functionals of the 4-volume element of the Universe. For them to be nonzero, the Universe should be finite in spacetime. If this matter is the standard model of particle physics, our mechanism prevents any of its vacuum energy, classical or quantum, from sourcing the curvature of the Universe. The mechanism is consistent with the large hierarchy between the Planck scale, electroweak scale, and curvature scale, and early Universe cosmology, including inflation. Consequences of our proposal are that the vacuum curvature of an old and large universe is not zero, but very small, that w DE â‰ƒâˆ’1 is a transient, and that the Universe will collapse in the future

### HyRec: A fast and highly accurate primordial hydrogen and helium recombination code

We present a state-of-the-art primordial recombination code, HyRec, including
all the physical effects that have been shown to significantly affect
recombination. The computation of helium recombination includes simple analytic
treatments of hydrogen continuum opacity in the He I 2 1P - 1 1S line, the He
I] 2 3P - 1 1S line, and treats feedback between these lines within the
on-the-spot approximation. Hydrogen recombination is computed using the
effective multilevel atom method, virtually accounting for an infinite number
of excited states. We account for two-photon transitions from 2s and higher
levels as well as frequency diffusion in Lyman-alpha with a full radiative
transfer calculation. We present a new method to evolve the radiation field
simultaneously with the level populations and the free electron fraction. These
computations are sped up by taking advantage of the particular sparseness
pattern of the equations describing the radiative transfer. The computation
time for a full recombination history is ~2 seconds. This makes our code well
suited for inclusion in Monte Carlo Markov chains for cosmological parameter
estimation from upcoming high-precision cosmic microwave background anisotropy
measurements.Comment: Version accepted by PRD. Numerical integration switches adapted to be
well behaved for a wide range of cosmologies (Sec. V E). HyRec is available
at http://www.tapir.caltech.edu/~yacine/hyrec/hyrec.htm

### Sequestering effects on and of vacuum decay

We consider phase transitions and their contributions to vacuum energy in the manifestly local theory of vacuum energy sequestering. We demonstrate that the absence of instabilities imposes constraints on the couplings of gravitating and nongravitating sectors, which can be satisfied in a large class of models. We further show by explicit construction that the vacuum energy contributions to the effective cosmological constant in the descendant vacua are generically strongly suppressed by the ratios of space-time volumes of parent and descendant geometries. This means that the cosmological constant in de Sitter descendant vacua remains insensitive to phase transitions which may have occurred in the course of its cosmic history

### Massive vector fields on the Schwarzschild spacetime: quasinormal modes and bound states

We study the propagation of a massive vector or Proca field on the
Schwarzschild spacetime. The field equations are reduced to a one-dimensional
wave equation for the odd-parity part of the field and two coupled equations
for the even-parity part of the field. We use numerical techniques based on
solving (scalar or matrix-valued) three-term recurrence relations to compute
the spectra of both quasi-normal modes and quasi-bound states, which have no
massless analogue, complemented in the latter case by a forward-integration
method. We study the radial equations analytically in both the near-horizon and
far-field regions and use a matching procedure to compute the associated
spectra in the small-mass limit. Finally, we comment on extending our results
to the Kerr geometry and its phenomenological relevance for hidden photons
arising e.g. in string theory compactifications.Comment: 15 pages, 8 figures; minor corrections, to be published in Phys. Rev.

### The Cosmological Evolution of Domain Wall Networks

We have studied the cosmological evolution of domain wall networks in two,
three and four spatial dimensions using high-resolution field theory
simulations. The dynamical range and number of our simulations is larger than
in previous works, but does not allow us to exclude previous hints of
deviations to the naively expected scale-invariant evolution. These results
therefore suggest that the approach of domain wall networks to linear scaling
is a much slower process than that of cosmic strings, which has been previously
characterized in detail.Comment: 7 pages, submitted to Phys Rev

### On the theory of the propagation of detonation in gaseous systems

The existing theory of detonation is critically examined. It is shown that the considerations with which the steady value of the velocity of detonation is chosen are not convincing. In connection with the problem of the process of the chemical reaction in a detonation wave, the objections raised against the conceptions of Le Chatelier and Vieille of the 19th century with regard to the ignition of the gas by the shock wave are refuted. On the basis of this concept, it is possible to give a rigorous foundation for the existing method of computing the detonation velocity. The distributions of the temperature, the pressure, and the velocity in the detonation wave front as the chemical reaction proceeds, are considered. On the assumption of the absence of losses, the pure compression of the gas in the shock wave at the start of the chemical reaction develops a temperature that is near the temperature of combustion of the given mixture at constant pressure

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