2,295 research outputs found
PMH14 Comparison of Medical Costs and Utilization Associated With Use of Ziprasidone and Olanzapine Among Schizophrenia and Bipolar Disorder Patients
Why non-superconducting metallic elements become superconducting under high pressure
We predict that simple metals and early transition metals that become
superconducting under high pressures will show a change in sign of their Hall
coefficient from negative to positive under pressure. If verified, this will
strongly suggest that hole carriers play a fundamental role in `conventional'
superconductivity, as predicted by the theory of hole superconductivity.Comment: Submitted to M2S-IX Tokyo 200
Matter wave functions and Yukawa couplings in F-theory Grand Unification
We study the local structure of zero mode wave functions of chiral matter
fields in F-theory unification. We solve the differential equations for the
zero modes derived from local Higgsing in the 8-dimensional parent action of
F-theory 7-branes. The solutions are found as expansions both in powers and
derivatives of the magnetic fluxes. Yukawa couplings are given by an overlap
integral of the three wave functions involved in the interaction and can be
calculated analytically. We provide explicit expressions for these Yukawas to
second order both in the flux and derivative expansions and discuss the effect
of higher order terms. We explicitly describe the dependence of the couplings
on the U(1) charges of the relevant fields, appropriately taking into account
their normalization. A hierarchical Yukawa structure is naturally obtained. The
application of our results to the understanding of the observed hierarchies of
quarks and leptons is discussed.Comment: Latex, 51 pages, 4 figures, typos corrected, note adde
Covariant anomaly and Hawking radiation from the modified black hole in the rainbow gravity theory
Recently, Banerjee and Kulkarni (R. Banerjee, S. Kulkarni, arXiv:0707.2449
[hep-th]) suggested that it is conceptually clean and economical to use only
the covariant anomaly to derive Hawking radiation from a black hole. Based upon
this simplified formalism, we apply the covariant anomaly cancellation method
to investigate Hawking radiation from a modified Schwarzschild black hole in
the theory of rainbow gravity. Hawking temperature of the gravity's rainbow
black hole is derived from the energy-momentum flux by requiring it to cancel
the covariant gravitational anomaly at the horizon. We stress that this
temperature is exactly the same as that calculated by the method of cancelling
the consistent anomaly.Comment: 5 page
Anomaly analysis of Hawking radiation from Kaluza-Klein black hole with squashed horizon
Considering gravitational and gauge anomalies at the horizon, a new method
that to derive Hawking radiations from black holes has been developed by
Wilczek et al. In this paper, we apply this method to non-rotating and rotating
Kaluza-Klein black holes with squashed horizon, respectively. For the rotating
case, we found that, after the dimensional reduction, an effective U(1) gauge
field is generated by an angular isometry. The results show that the gauge
current and energy-momentum tensor fluxes are exactly equivalent to Hawking
radiation from the event horizon.Comment: 15 pages, no figures, the improved version, accepted by Eur. Phys. J.
F-theory uplifts and GUTs
We study the F-theory uplift of Type IIB orientifold models on compact
Calabi-Yau threefolds containing divisors which are del Pezzo surfaces. We
consider two examples defined via del Pezzo transitions of the quintic. The
first model has an orientifold projection leading to two disjoint O7-planes and
the second involution acts via an exchange of two del Pezzo surfaces. The two
uplifted fourfolds are generically singular with minimal gauge enhancements
over a divisor and, respectively, a curve in the non-Fano base. We study
possible further degenerations of the elliptic fiber leading to F-theory GUT
models based on subgroups of E8.Comment: 28 pages, 5 tables; v2: typos removed, minor correction
Unification, KK-thresholds and the top Yukawa coupling in F-theory GUTs
In a class of F-theory SU(5) GUTs the low energy chiral mass spectrum is
obtained from rank one fermion mass textures with a hierarchical structure
organised by U(1) symmetries embedded in the exceptional E_8 group. In these
theories chiral fields reside on matter `curves' and the tree level masses are
computed from integrals of overlapping wavefuctions of the particles at the
triple intersection points. This calculation requires knowledge of the exact
form of the wavefuctions. In this work we propose a way to obtain a reliable
estimate of the various quantities which determine the strength of the Yukawa
couplings. We use previous analysis of KK threshold effects to determine the
(ratios of) heavy mass scales of the theory which are involved in the
normalization of the wave functions. We consider similar effects from the
chiral spectrum of these models and discuss possible constraints on the
emerging matter content. In this approach, we find that the Yukawa couplings
can be determined solely from the U(1) charges of the states in the
`intersection' and the torsion which is a topological invariant quantity. We
apply the results to a viable SU(5) model with minimal spectrum which satisfies
all the constraints imposed by our analysis. We use renormalization group
analysis to estimate the top and bottom masses and find that they are in
agreement with the experimental values.Comment: 28 pages, 2 figure
Recent experimental results in sub- and near-barrier heavy ion fusion reactions
Recent advances obtained in the field of near and sub-barrier heavy-ion
fusion reactions are reviewed. Emphasis is given to the results obtained in the
last decade, and focus will be mainly on the experimental work performed
concerning the influence of transfer channels on fusion cross sections and the
hindrance phenomenon far below the barrier. Indeed, early data of sub-barrier
fusion taught us that cross sections may strongly depend on the low-energy
collective modes of the colliding nuclei, and, possibly, on couplings to
transfer channels. The coupled-channels (CC) model has been quite successful in
the interpretation of the experimental evidences. Fusion barrier distributions
often yield the fingerprint of the relevant coupled channels. Recent results
obtained by using radioactive beams are reported. At deep sub-barrier energies,
the slope of the excitation function in a semi-logarithmic plot keeps
increasing in many cases and standard CC calculations over-predict the cross
sections. This was named a hindrance phenomenon, and its physical origin is
still a matter of debate. Recent theoretical developments suggest that this
effect, at least partially, may be a consequence of the Pauli exclusion
principle. The hindrance may have far-reaching consequences in astrophysics
where fusion of light systems determines stellar evolution during the carbon
and oxygen burning stages, and yields important information for exotic
reactions that take place in the inner crust of accreting neutron stars.Comment: 40 pages, 63 figures, review paper accepted for EPJ
Black Hole Entropy: From Shannon to Bekenstein
In this note we have applied directly the Shannon formula for information
theory entropy to derive the Black Hole (Bekenstein-Hawking) entropy. Our
analysis is semi-classical in nature since we use the (recently proposed [8])
quantum mechanical near horizon mode functions to compute the tunneling
probability that goes in to the Shannon formula, following the general idea of
[5]. Our framework conforms to the information theoretic origin of Black Hole
entropy, as originally proposed by Bekenstein.Comment: 9 pages Latex, Comments are welcome; Thoroughly revised version,
reference and acknowledgements sections enlarged, numerical error in final
result corrected, no major changes, to appear in IJT
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