3,406 research outputs found
Rigid Limit in N=2 Supergravity and Weak-Gravity Conjecture
We analyze the coupled N=2 supergravity and Yang-Mills system using
holomorphy, near the rigid limit where the former decouples from the latter. We
find that there appears generically a new mass scale around g M_{pl} where g is
the gauge coupling constant and M_{pl} is the Planck scale. This is in accord
with the weak-gravity conjecture proposed recently. We also study the scale
dependence of the gauge theory prepotential from its embedding into
supergravity.Comment: 17 pages, minor correction
Binding between endohedral Na atoms in Si clathrate I; a first principles study
We investigate the binding nature of the endohedral sodium atoms with the
ensity functional theory methods, presuming that the clathrate I consists of a
sheaf of one-dimensional connections of Na@Si cages interleaved in three
perpendicular directions. Each sodium atom loses 30% of the 3s charge to
the frame, forming an ionic bond with the cage atoms; the rest of the electron
contributes to the covalent bond between the nearest Na atoms. The presumption
is proved to be valid; the configuration of the two Na atoms in the nearest
Si cages is more stable by 0.189 eV than that in the Si and
Si cages. The energy of the beads of the two distorted Na atoms is more
stable by 0.104 eV than that of the two infinitely separated Na atoms. The
covalent bond explains both the preferential occupancies in the Si cages
and the low anisotropic displacement parameters of the endohedral atoms in the
Si cages in the [100] directions of the clathrate I.Comment: First page: Affiliation added to PDF and PS versio
The Renormalization of Non-Commutative Field Theories in the Limit of Large Non-Commutativity
We show that renormalized non-commutative scalar field theories do not reduce
to their planar sector in the limit of large non-commutativity. This follows
from the fact that the RG equation of the Wilson-Polchinski type which
describes the genus zero sector of non-commutative field theories couples
generic planar amplitudes with non-planar amplitudes at exceptional values of
the external momenta. We prove that the renormalization problem can be
consistently restricted to this set of amplitudes. In the resulting
renormalized theory non-planar divergences are treated as UV divergences
requiring appropriate non-local counterterms. In 4 dimensions the model turns
out to have one more relevant (non-planar) coupling than its commutative
counterpart. This non-planar coupling is ``evanescent'': although in the
massive (but not in the massless) case its contribution to planar amplitudes
vanishes when the floating cut-off equals the renormalization scale, this
coupling is needed to make the Wilsonian effective action UV finite at all
values of the floating cut-off.Comment: 35 pages, 8 figures; typos correcte
Hermitian Matrix Model with Plaquette Interaction
We study a hermitian -matrix model with plaquette interaction,
. By means of a conformal transformation we rewrite the
model as an model on a random lattice with a non polynomial potential.
This allows us to solve the model exactly. We investigate the critical
properties of the plaquette model and find that for the model
belongs to the same universality class as the model on a random lattice.Comment: 15 pages, no figures, two references adde
High Sensitivity Search for v_e’s from the Sun and Other Sources at KamLAND
Data corresponding to a KamLAND detector exposure of 0.28 kton yr has been used to search for ν̅ _e’s in the energy range 8.3 < E_(ν̅e) < 14.8 MeV. No candidates were found for an expected background of 1.1±0.4 events. This result can be used to obtain a limit on ν̅_e fluxes of any origin. Assuming that all ν̅_e flux has its origin in the Sun and has the characteristic ^8B solar ν_e energy spectrum, we obtain an upper limit of 3.7×10^2 cm^(-2) ^(s-1) (90% C.L.) on the ν̅_e flux. We interpret this limit, corresponding to 2.8×10^(-4) of the standard solar model ^8B ν_e flux, in the framework of spin-flavor precession and neutrino decay models
Local demands on sterile neutrinos
In a model independent manner, we explore the local implications of a single
neutrino oscillation measurement which cannot be reconciled within a
three-neutrino theory. We examine this inconsistency for a single region of
baseline to neutrino energy . Assuming that sterile neutrinos account for
the anomaly, we find that the {\it local} demands of this datum can require the
addition to the theory of one to three sterile neutrinos. We examine the
constraints which can be used to determine when more than one neutrino would be
required. The results apply only to a given region of . The question of
the adequacy of the sterile neutrinos to satisfy a global analysis is not
addressed here. Finally, using the results of a 3+2 analysis, we indicate
values for unknown mixing matrix elements which would require two sterile
neutrinos due to local demands only.Comment: 11 pages, 1 figure, discussion adde
Lorentz Invariance and Origin of Symmetries
In this letter we reconsider the role of Lorentz invariance in the dynamical
generation of the observed internal symmetries. We argue that, generally,
Lorentz invariance can only be imposed in the sense that all Lorentz
non-invariant effects caused by the spontaneous breakdown of Lorentz symmetry
are physically unobservable. Remarkably, the application of this principle to
the most general relativistically invariant Lagrangian, with arbitrary
couplings for all the fields involved, leads by itself to the appearance of a
symmetry and, what is more, to the massless vector fields gauging this symmetry
in both Abelian and non-Abelian cases. In contrast, purely global symmetries
are only generated as accidental consequences of the gauge symmetry.Comment: 10 page LaTeX fil
The non-compact elliptic genus: mock or modular
We analyze various perspectives on the elliptic genus of non-compact
supersymmetric coset conformal field theories with central charge larger than
three. We calculate the holomorphic part of the elliptic genus via a free field
description of the model, and show that it agrees with algebraic expectations.
The holomorphic part of the elliptic genus is directly related to an
Appell-Lerch sum and behaves anomalously under modular transformation
properties. We analyze the origin of the anomaly by calculating the elliptic
genus through a path integral in a coset conformal field theory. The path
integral codes both the holomorphic part of the elliptic genus, and a
non-holomorphic remainder that finds its origin in the continuous spectrum of
the non-compact model. The remainder term can be shown to agree with a function
that mathematicians introduced to parameterize the difference between mock
theta functions and Jacobi forms. The holomorphic part of the elliptic genus
thus has a path integral completion which renders it non-holomorphic and
modular.Comment: 13 page
Neutrino texture saturating the CP asymmetry
We study a neutrino mass texture which can explain the neutrino oscillation
data and also saturate the upper bound of the CP asymmetry in the
leptogenesis. We consider the thermal and non-thermal leptogenesis based on the
right-handed neutrino decay in this model. A lower bound of the reheating
temperature required for the explanation of the baryon number asymmetry is
estimated as GeV for the thermal leptogenesis and GeV for
the non-thermal one.It can be lower than the upper bound of the reheating
temperature imposed by the cosmological gravitino problem. An example of the
construction of the discussed texture is also presented.Comment: 23 pages, 6 figure
On the Genus Two Free Energies for Semisimple Frobenius Manifolds
We represent the genus two free energy of an arbitrary semisimple Frobenius
manifold as a sum of contributions associated with dual graphs of certain
stable algebraic curves of genus two plus the so-called "genus two G-function".
Conjecturally the genus two G-function vanishes for a series of important
examples of Frobenius manifolds associated with simple singularities as well as
for -orbifolds with positive Euler characteristics. We explain the
reasons for such Conjecture and prove it in certain particular cases.Comment: 37 pages, 3 figures, V2: the published versio
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