18,288 research outputs found
Peccei-Quinn Relaxion
The relaxation mechanism, which solves the electroweak hierarchy problem
without relying on TeV scale new physics, crucially depends on how a
Higgs-dependent back-reaction potential is generated. In this paper, we suggest
a new scenario in which the scalar potential induced by the QCD anomaly is
responsible both for the relaxation mechanism and the Peccei-Quinn mechanism to
solve the strong CP problem. The key idea is to introduce the relaxion and the
QCD axion whose cosmic evolutions become quite different depending on an
inflaton-dependent scalar potential. Our scheme raises the cutoff scale of the
Higgs mass up to 10^7 GeV, and allows reheating temperature higher than the
electroweak scale as would be required for viable cosmology. In addition, the
QCD axion can account for the observed dark matter of the universe as produced
by the conventional misalignment mechanism. We also consider the possibility
that the couplings of the Standard Model depend on the inflaton and become
stronger during inflation. In this case, the relaxation can be implemented with
a sub-Planckian field excursion of the relaxion for a cutoff scale below 10
TeV.Comment: 14 pages, 1 figure; minor changes, accepted for publication in JHE
Effects of squeezing on quantum nonlocality of superpositions of coherent states
We analyze effects of squeezing upon superpositions of coherent states (SCSs)
and entangled coherent states (ECSs) for Bell-inequality tests. We find that
external squeezing can always increase the degrees of Bell violations, if the
squeezing direction is properly chosen, for the case of photon parity
measurements. On the other hand, when photon on/off measurements are used, the
squeezing operation can enhance the degree of Bell violations only for moderate
values of amplitudes and squeezing. We point out that a significant improvement
is required over currently available squeezed SCSs in order to directly
demonstrate a Bell-inequality violation in a real experiment.Comment: 7 pages, 4 figures, accepted for publication in Phys. Rev.
A map of the non-thermal WIMP
We study the effect of the elastic scattering on the non-thermal WIMP, which
is produced by direct decay of heavy particles at the end of reheating. The
non-thermal WIMP becomes important when the reheating temperature is well below
the freeze-out temperature. Usually, two limiting cases have been considered.
One is that the produced high energetic dark matter particles are quickly
thermalized due to the elastic scattering with background radiations. The
corresponding relic abundance is determined by the thermally averaged
annihilation cross-section at the reheating temperature. The other one is that
the initial abundance is too small for the dark matter to annihilate so that
the final relic is determined by the initial amount itself. We study the
regions between these two limits, and show that the relic density depends not
only on the annihilation rate, but also on the elastic scattering rate.
Especially, the relic abundance of the p-wave annihilating dark matter
crucially relies on the elastic scattering rate because the annihilation
cross-section is sensitive to the dark matter velocity. We categorize the
parameter space into several regions where each region has distinctive
mechanism for determining the relic abundance of the dark matter at the present
Universe. The consequence on the (in)direct detection is also studied.Comment: 9 pages, 5 figures; v2: discussion improved, matches version
published in PL
Effects of depolarizing quantum channels on BB84 and SARG04 quantum cryptography protocols
We report experimental studies on the effect of the depolarizing quantum
channel on weak-pulse BB84 and SARG04 quantum cryptography. The experimental
results show that, in real world conditions in which channel depolarization
cannot be ignored, BB84 should perform better than SARG04.Comment: 4 pages, 4 figure
Brain-Switches for Asynchronous Brain−Computer Interfaces: A Systematic Review
A brain–computer interface (BCI) has been extensively studied to develop a novel communication system for disabled people using their brain activities. An asynchronous BCI system is more realistic and practical than a synchronous BCI system, in that, BCI commands can be generated whenever the user wants. However, the relatively low performance of an asynchronous BCI system is problematic because redundant BCI commands are required to correct false-positive operations. To significantly reduce the number of false-positive operations of an asynchronous BCI system, a two-step approach has been proposed using a brain-switch that first determines whether the user wants to use an asynchronous BCI system before the operation of the asynchronous BCI system. This study presents a systematic review of the state-of-the-art brain-switch techniques and future research directions. To this end, we reviewed brain-switch research articles published from 2000 to 2019 in terms of their (a) neuroimaging modality, (b) paradigm, (c) operation algorithm, and (d) performance
Minimalist's Linux Cluster
Using barebone PC components and NIC's, we construct a linux cluster which
has 2-dimensional mesh structure. This cluster has smaller footprint, is less
expensive, and use less power compared to conventional linux cluster. Here, we
report our experience in building such a machine and discuss our current
lattice project on the machine.Comment: 3 pages, 2 figures, Proceedings of the Lattice 03 Conference
(Tsukuba, Japan
Adiabatic Electroweak Baryogenesis Driven by an Axion-like Particle
An axion-like particle (ALP) offers a new direction in electroweak
baryogenesis because the periodic nature enables it to trigger a strong
first-order phase transition insensitively to the decay constant . For
much above TeV, the ALP-induced electroweak phase transition is approximately
described by adiabatic processes, distinguishing our scenario for electroweak
baryogenesis from the conventional ones. We show that, coupled to the
electroweak anomaly, the ALP can naturally realize spontaneous electroweak
baryogenesis to solve the matter-antimatter asymmetry problem for in the
range between about GeV and GeV. In such an ALP window, the
violation for baryogenesis is totally free from the experimental constraints,
especially from the recently improved limit on the electron electric dipole
moment. Future searches for ALPs could probe our scenario while revealing the
connection between electroweak symmetry breaking and baryogenesis.Comment: 12 pages, 5 figures, appendices added, published versio
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