1,008 research outputs found
Holomorphic anomaly and matrix models
The genus g free energies of matrix models can be promoted to modular
invariant, non-holomorphic amplitudes which only depend on the geometry of the
classical spectral curve. We show that these non-holomorphic amplitudes satisfy
the holomorphic anomaly equations of Bershadsky, Cecotti, Ooguri and Vafa. We
derive as well holomorphic anomaly equations for the open string sector. These
results provide evidence at all genera for the Dijkgraaf--Vafa conjecture
relating matrix models to type B topological strings on certain local
Calabi--Yau threefolds.Comment: 23 pages, LaTex, 3 figure
Interacting fermions and N=2 Chern-Simons-matter theories
The partition function on the three-sphere of N=3 Chern-Simons-matter
theories can be formulated in terms of an ideal Fermi gas. In this paper we
show that, in theories with N=2 supersymmetry, the partition function
corresponds to a gas of interacting fermions in one dimension. The large N
limit is the thermodynamic limit of the gas and it can be analyzed with the
Hartree and Thomas-Fermi approximations, which lead to the known large N
solutions of these models. We use this interacting fermion picture to analyze
in detail N=2 theories with one single node. In the case of theories with no
long-range forces we incorporate exchange effects and argue that the partition
function is given by an Airy function, as in N=3 theories. For the theory with
g adjoint superfields and long-range forces, the Thomas-Fermi approximation
leads to an integral equation which determines the large N, strongly coupled
R-charge.Comment: 29 pages, 4 figure
Crystal structure of N-(2-hydroxy-5-methylphenyl)benzamide
In the title compound, C14H13NO2, the mean plane of the non-H atoms of the central amide fragment C-N-C(=O)-C (r.m.s. deviation = 0.029 Å) forms dihedral angles of 5.63 (6) and 10.20 (5)° with the phenyl and hydroxyphenyl rings, respectively. A short intramolecular N-H...O contact is present. In the crystal, the molecules are linked by O-H...O hydrogen bonds to generate C(7) chains along [100]. The chains are reinforced by weak C-H...O contacts, which together with the O-H...O bonds lead to R22(7) loops. Very weak N-H...O interactions link the molecules into inversion dimers
Exact Results in ABJM Theory from Topological Strings
Recently, Kapustin, Willett and Yaakov have found, by using localization
techniques, that vacuum expectation values of Wilson loops in ABJM theory can
be calculated with a matrix model. We show that this matrix model is closely
related to Chern-Simons theory on a lens space with a gauge supergroup. This
theory has a topological string large N dual, and this makes possible to solve
the matrix model exactly in the large N expansion. In particular, we find the
exact expression for the vacuum expectation value of a 1/6 BPS Wilson loop in
the ABJM theory, as a function of the 't Hooft parameters, and in the planar
limit. This expression gives an exact interpolating function between the weak
and the strong coupling regimes. The behavior at strong coupling is in precise
agreement with the prediction of the AdS string dual. We also give explicit
results for the 1/2 BPS Wilson loop recently constructed by Drukker and
TrancanelliComment: 18 pages, two figures, small misprints corrected and references
added, final version to appear in JHE
Decoupling A and B model in open string theory -- Topological adventures in the world of tadpoles
In this paper we analyze the problem of tadpole cancellation in open
topological strings. We prove that the inclusion of unorientable worldsheet
diagrams guarantees a consistent decoupling of A and B model for open
superstring amplitudes at all genera. This is proven by direct microscopic
computation in Super Conformal Field Theory. For the B-model we explicitly
calculate one loop amplitudes in terms of analytic Ray-Singer torsions of
appropriate vector bundles and obtain that the decoupling corresponds to the
cancellation of D-brane and orientifold charges. Local tadpole cancellation on
the worldsheet then guarantees the decoupling at all loops. The holomorphic
anomaly equations for open topological strings at one loop are also obtained
and compared with the results of the Quillen formula
Direct Integration of the Topological String
We present a new method to solve the holomorphic anomaly equations governing
the free energies of type B topological strings. The method is based on direct
integration with respect to the non-holomorphic dependence of the amplitudes,
and relies on the interplay between non-holomorphicity and modularity
properties of the topological string amplitudes. We develop a formalism valid
for any Calabi-Yau manifold and we study in detail two examples, providing
closed expressions for the amplitudes at low genus, as well as a discussion of
the boundary conditions that fix the holomorphic ambiguity. The first example
is the non-compact Calabi-Yau underlying Seiberg-Witten theory and its
gravitational corrections. The second example is the Enriques Calabi-Yau, which
we solve in full generality up to genus six. We discuss various aspects of this
model: we obtain a new method to generate holomorphic automorphic forms on the
Enriques moduli space, we write down a new product formula for the fiber
amplitudes at all genus, and we analyze in detail the field theory limit. This
allows us to uncover the modularity properties of SU(2), N=2 super Yang-Mills
theory with four massless hypermultiplets.Comment: 75 pages, 3 figure
AuNx stabilization with interstitial nitrogen atoms: A Density Functional Theory Study
Researchers have been studying 4d and 5d Series Transition Metal Nitrides lately as a result of the experimental production of AuN, PtN, CuN. In this paper, we used the Density Functional Theory (DFT) implementing a pseudopotential plane-wave method to study the incorporation of nitrogen atoms in the face-centered cube (fcc) lattice of gold (Au). First, we took the fcc structure of gold, and gradually located the nitrogen atoms in tetrahedral (TH) and octahedral (OH) interstitial sites. AuN stabilized in: 2OH (30%), 4OH and 4TH (50%), 4OH - 2TH (close to the wurtzite structure) and 6TH (60%). This leads us to think that AuN behaves like a Transition Metal Nitride since the nitrogen atoms look for tetrahedral sites. © Published under licence by IOP Publishing Ltd
Black Holes and Large Order Quantum Geometry
We study five-dimensional black holes obtained by compactifying M theory on
Calabi-Yau threefolds. Recent progress in solving topological string theory on
compact, one-parameter models allows us to test numerically various conjectures
about these black holes. We give convincing evidence that a microscopic
description based on Gopakumar-Vafa invariants accounts correctly for their
macroscopic entropy, and we check that highly nontrivial cancellations -which
seem necessary to resolve the so-called entropy enigma in the OSV conjecture-
do in fact occur. We also study analytically small 5d black holes obtained by
wrapping M2 branes in the fiber of K3 fibrations. By using heterotic/type II
duality we obtain exact formulae for the microscopic degeneracies in various
geometries, and we compute their asymptotic expansion for large charges.Comment: 42 pages, 20 eps figures, small correction
Unquenched flavor and tropical geometry in strongly coupled Chern-Simons-matter theories
We study various aspects of the matrix models calculating free energies and
Wilson loop observables in supersymmetric Chern-Simons-matter theories on the
three-sphere. We first develop techniques to extract strong coupling results
directly from the spectral curve describing the large N master field. We show
that the strong coupling limit of the gauge theory corresponds to the so-called
tropical limit of the spectral curve. In this limit, the curve degenerates to a
planar graph, and matrix model calculations reduce to elementary line integrals
along the graph. As an important physical application of these tropical
techniques, we study N=3 theories with fundamental matter, both in the quenched
and in the unquenched regimes. We calculate the exact spectral curve in the
Veneziano limit, and we evaluate the planar free energy and Wilson loop
observables at strong coupling by using tropical geometry. The results are in
agreement with the predictions of the AdS duals involving tri-Sasakian
manifoldsComment: 32 pages, 7 figures. v2: small corrections, added an Appendix on the
relation with the approach of 1011.5487. v3: further corrections and
clarifications, final version to appear in JHE
Psychological and behavioral acculturation in a social network of Mexican Americans in the United States and use of dental services
Objectives
We used data from the TalaSurvey study to examine associations between dental health experiences, social network characteristics, and levels of behavioral and psychological acculturation in one location in the American Midwest.
Methods
Starting in parishes and community organizations, we identified adults of Mexican origin living in Indianapolis, who were 1st- or 2nd-generation immigrants from Tala, Mexico. Using a social networks methodology and following extensive formative research, we created an egocentric social network survey and administered it via face-to-face interviews. We identified the peers (alters) in interviewees’ (egos) personal networks. We asked egos about multiple oral health and dental care variables for self and for alters. Acculturation (psychological and behavioral) was measured with a validated tool. Through logistic and negative binomial regression, we examined the effects of acculturation and network composition on ego's dental insurance status, dental office visits, and the reason for most recent dental office visit.
Results
A total of 332 egos (mean age 36; 63% female) were interviewed: 90% were born in Mexico; 45% had completed elementary school or lower; and most had low income. Each ego named 3.9 (SD±1.9) alters in his/her personal network, for a total of 1299 alters (mean age 39; 61% female). Both behavioral acculturation and psychological acculturation were moderately associated with dental insurance coverage, and greater behavioral acculturation predicted more frequent dental care. More psychologically acculturated egos were more likely to seek preventive care. Further, egos with more highly educated networks sought care more frequently and for preventive purposes, net of ego's own education and acculturation.
Conclusions
This study contextualizes acculturation of Mexican Americans within the personal networks in which oral health discussion takes place. The findings underscore the critical importance of acculturation and social network factors in shaping a subgroup of Latinos’ orientation toward dental care
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