1,116 research outputs found
511 keV line and diffuse gamma rays from moduli
We obtain the spectrum of gamma ray emissions from the moduli whose decay
into accounts for the 511 keV line observed by SPI/INTERGRAL. The
moduli emit gamma rays through internal bremsstrahlung, and also decay directly
into two gammas via tree and/or one-loop diagrams. We show that the internal
bremsstahlung constrains the mass of the moduli below MeV
model-independently. On the other hand, the flux of two gammas directly decayed
from the moduli through one loop diagrams will exceed the observed galactic
diffuse gamma-ray background if the moduli mass exceeds MeV in the
typical situation. Moreover, forthcoming analysis of SPI data in the range of
1-8 MeV may detect the line emisson with the energy half the moduli mass in the
near future, which confirms the decaying moduli scenario.Comment: 6 pages, 5 figures, published versio
Smallness of Baryon Asymmetry from Split Supersymmetry
The smallness of the baryon asymmetry in our universe is one of the greatest
mysteries and may originate from some profound physics beyond the standard
model. We investigate the Affleck-Dine baryogenesis in split supersymmetry, and
find that the smallness of the baryon asymmetry is directly related to the
hierarchy between the supersymmetry breaking squark/slepton masses and the weak
scale. Put simply, the baryon asymmetry is small because of the split mass
spectrum.Comment: 4 pages, no figur
Affleck-Dine mechanism with negative thermal logarithmic potential
We investigate whether the Affleck-Dine (AD) mechanism works when the
contribution of the two-loop thermal correction to the potential is negative in
the gauge-mediated supersymmetry breaking models. The AD field is trapped far
away from the origin by the negative thermal correction for a long time until
the temperature of the universe becomes low enough. The most striking feature
is that the Hubble parameter becomes much smaller than the mass scale of the
radial component of the AD field, during the trap. Then, the amplitude of the
AD field decreases so slowly that the baryon number is not fixed even after the
onset of radial oscillation. The resultant baryon asymmetry crucially depends
on whether the Hubble parameter, , is larger than the mass scale of the
phase component of the AD field, , at the beginning of oscillation.
If holds, the formation of Q balls plays an essential role to
determine the baryon number, which is found to be washed out due to the
nonlinear dynamics of Q-ball formation. On the other hand, if
holds, it is found that the dynamics of Q-ball formation does not affect the
baryon asymmetry, and that it is possible to generate the right amount of the
baryon asymmetry.Comment: 18 pages, RevTeX4, 9 postscript figures included, final version to
appear in Phys.Rev.
On the Moduli Problem and Baryogenesis in Gauge-mediated SUSY Breaking Models
We investigate whether the Affleck-Dine mechanism can produce sufficient
baryon number of the universe in the gauge-mediated SUSY breaking models, while
evading the cosmological moduli problem by late-time entropy production. We
find that the Q-ball formation renders the scenario very difficult to work,
irrespective of the detail mechanism of the entropy production.Comment: 11 pages, RevTeX, 5 postscript figures include
Q-ball formation in the wake of Hubble-induced radiative corrections
We discuss some interesting aspects of the -ball formation during the
early oscillations of the flat directions. These oscillations are triggered by
the running of soft stemming from the nonzero energy density
of the Universe. However, this is quite different from the standard -ball formation. The running in presence of gauge and Yukawa couplings
becomes strong if is sufficiently large. Moreover, the -balls which are formed during the early oscillations constantly evolve, due
to the redshift of the Hubble-induced soft mass, until the low-energy
supersymmtery breaking becomes dominant. For smaller , -balls are not formed during early oscillations because of the shrinking of
the instability band due to the Hubble expansion. In this case the -balls are formed only at the weak scale, but typically carry smaller
charges, as a result of their amplitude redshift. Therefore, the Hubble-induced
corrections to the flat directions give rise to a successful -ball
cosmology.Comment: 7 revtex pages, few references corrected and added, final version to
appear in Phys. Rev.
Isocurvature fluctuations in Affleck-Dine mechanism and constraints on inflation models
We reconsider the Affleck-Dine mechanism for baryogenesis and show that the
baryonic isocurvature fluctuations are generated in many inflation models in
supergravity. The inflationary scale and the reheating temperature must satisfy
certain constraints to avoid too large baryonic isocurvature fluctuations.Comment: 18 pages, 1 figur
Momentum-Dependent Hybridization Gap and dispersive in-gap state of The Kondo Semiconductor SmB6
We report the temperature-dependent three-dimensional angle-resolved
photoemission spectra of the Kondo semiconductor SmB. We found a difference
in the temperature dependence of the peaks at the X and points, due to
hybridization between the Sm 5d conduction band and the nearly localized Sm 4f
state. The peak intensity at the X point has the same temperature dependence as
the valence transition below 120 K, while that at the point is
consistent with the magnetic excitation at Q=(0.5,0.5,0.5) below 30 K. This
suggests that the hybridization with the valence transition mainly occurs at
the X point, and the initial state of the magnetic excitation is located at the
point.Comment: 5 pages, 3 figure
Optical RKKY Interaction between Charged Semiconductor Quantum Dots
We show how a spin interaction between electrons localized in neighboring
quantum dots can be induced and controlled optically. The coupling is generated
via virtual excitation of delocalized excitons and provides an efficient
coherent control of the spins. This quantum manipulation can be realized in the
adiabatic limit and is robust against decoherence by spontaneous emission.
Applications to the realization of quantum gates, scalable quantum computers,
and to the control of magnetization in an array of charged dots are proposed.Comment: 4 pages, 2 figure
Q-ball formation in the gravity-mediated SUSY breaking scenario
We study the formation of Q-balls which are made of flat directions that
appear in the supersymmetric extension of the standard model in the context of
gravity-mediated supersymmetry breaking. The full non-linear calculations for
the dynamics of the complex scalar field are made. Since the scalar potential
in this model is flatter than \phi^2, we have found that fluctuations develop
and go non-linear to form non-topological solitons, Q-balls. The size of a
Q-ball is determined by the most amplified mode, which is completely determined
by the model parameters. On the other hand, the charge of Q-balls depends
linearly on the initial charge density of the Affleck-Dine (AD) field. Almost
all the charges are absorbed into Q-balls, and only a tiny fraction of the
charges is carried by a relic AD field. It may lead to some constraints on the
baryogenesis and/or parameters in the particle theory. The peculiarity of
gravity-mediation is the moving Q-balls. This results in collisions between
Q-balls. It may increase the charge of Q-balls, and change its fate.Comment: 9 pages, RevTex, 11 postscript figures included, to appear in Phys.
Rev.
Entropy production by Q-ball decay for diluting long-lived charged particles
The cosmic abundance of a long-lived charged particle such as a stau is
tightly constrained by the catalyzed big bang nucleosynthesis. One of the ways
to evade the constraints is to dilute those particles by a huge entropy
production. We evaluate the dilution factor in a case that non-relativistic
matter dominates the energy density of the universe and decays with large
entropy production. We find that large Q balls can do the job, which is
naturally produced in the gauge-mediated supersymmetry breaking scenario.Comment: 8 pages, 1 figur
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