567 research outputs found
Microscopic quantum superpotential in N=1 gauge theories
We consider the N=1 super Yang-Mills theory with gauge group U(N), adjoint
chiral multiplet X and tree-level superpotential Tr W(X). We compute the
quantum effective superpotential W_mic as a function of arbitrary off-shell
boundary conditions at infinity for the scalar field X. This effective
superpotential has a remarkable property: its critical points are in one-to-one
correspondence with the full set of quantum vacua of the theory, providing in
particular a unified picture of solutions with different ranks for the low
energy gauge group. In this sense, W_mic is a good microscopic effective
quantum superpotential for the theory. This property is not shared by other
quantum effective superpotentials commonly used in the literature, like in the
strong coupling approach or the glueball superpotentials. The result of this
paper is a first step in extending Nekrasov's microscopic derivation of the
Seiberg-Witten solution of N=2 super Yang-Mills theories to the realm of N=1
gauge theories.Comment: 23 pages, 1 figure; typos corrected, version to appear in JHE
The Proof of the Dijkgraaf-Vafa Conjecture and application to the mass gap and confinement problems
Using generalized Konishi anomaly equations, it is known that one can
express, in a large class of supersymmetric gauge theories, all the chiral
operators expectation values in terms of a finite number of a priori arbitrary
constants. We show that these constants are fully determined by the requirement
of gauge invariance and an additional anomaly equation. The constraints so
obtained turn out to be equivalent to the extremization of the Dijkgraaf-Vafa
quantum glueball superpotential, with all terms (including the
Veneziano-Yankielowicz part) unambiguously fixed. As an application, we fill
non-trivial gaps in existing derivations of the mass gap and confinement
properties in super Yang-Mills theories.Comment: 31 pages, 1 figure; v2: typos corrected; references, a note on
Kovner-Shifman vacua (section 4.3) and a few clarifying comments in Section 3
added; v3: cosmetic changes, JHEP versio
Glueball operators and the microscopic approach to N=1 gauge theories
We explain how to generalize Nekrasov's microscopic approach to N=2 gauge
theories to the N=1 case, focusing on the typical example of the U(N) theory
with one adjoint chiral multiplet X and an arbitrary polynomial tree-level
superpotential Tr W(X). We provide a detailed analysis of the generalized
glueball operators and a non-perturbative discussion of the Dijkgraaf-Vafa
matrix model and of the generalized Konishi anomaly equations. We compute in
particular the non-trivial quantum corrections to the Virasoro operators and
algebra that generate these equations. We have performed explicit calculations
up to two instantons, that involve the next-to-leading order corrections in
Nekrasov's Omega-background.Comment: 38 pages, 1 figure and 1 appendix included; v2: typos and the list of
references corrected, version to appear in JHE
Identification of Amino Acid Sequences with Good Folding Properties in an Off-Lattice Model
Folding properties of a two-dimensional toy protein model containing only two
amino-acid types, hydrophobic and hydrophilic, respectively, are analyzed. An
efficient Monte Carlo procedure is employed to ensure that the ground states
are found. The thermodynamic properties are found to be strongly sequence
dependent in contrast to the kinetic ones. Hence, criteria for good folders are
defined entirely in terms of thermodynamic fluctuations. With these criteria
sequence patterns that fold well are isolated. For 300 chains with 20 randomly
chosen binary residues approximately 10% meet these criteria. Also, an analysis
is performed by means of statistical and artificial neural network methods from
which it is concluded that the folding properties can be predicted to a certain
degree given the binary numbers characterizing the sequences.Comment: 15 pages, 8 Postscript figures. Minor change
Extensive Modeling of a Coaxial Stub Resonator for Online Fingerprinting of Fluids
A straightforward method of extensive modeling of a lossy stub resonator system for online fingerprinting of fluids is presented in this paper. The proposed model solves the telegrapher's equations including the skin effect and dielectric losses and describes the amplitude versus frequency response of lossy coaxial stub resonators with a fluid under investigation as dielectric. The adequacy of the method is demonstrated by comparing simulations with experimentally obtained data. Even though we applied the model to a coaxial stub resonator for the online fingerprinting of fluids (e.g., for water quality monitoring), the potential applicability of the method reaches further. Indeed, the method introduced here may be useful for different types of sensors based on lossy transmission line theor
Extended N=1 super Yang-Mills theory
We solve a generalization of ordinary N=1 super Yang-Mills theory with gauge
group U(N) and an adjoint chiral multiplet X for which we turn on both an
arbitrary tree-level superpotential term \int d^{2}\theta Tr W(X) and an
arbitrary field-dependent gauge kinetic term \int d^{2}\theta Tr
V(X)W^{\alpha}W_{\alpha}. When W=0, the model reduces to the extended
Seiberg-Witten theory recently studied by Marshakov and Nekrasov. We use two
different points of view: a ''macroscopic'' approach, using generalized anomaly
equations, the Dijkgraaf-Vafa matrix model and the glueball superpotential; and
the recently proposed ''microscopic'' approach, using Nekrasov's sum over
colored partitions and the quantum microscopic superpotential. The two
formalisms are based on completely different sets of variables and statistical
ensembles. Yet it is shown that they yield precisely the same gauge theory
correlators. This beautiful mathematical equivalence is a facet of the
open/closed string duality. A full microscopic derivation of the
non-perturbative N=1 gauge dynamics follows.Comment: 47 pages, 3 figures, 2 appendices; v2: typos and references
corrected, published in JHE
Identification of occult metastases of medullary thyroid carcinoma by pentagastrin-stimulated intravenous calcitonin sampling followed by targeted surgery
BACKGROUND: High calcitonin (CT) serum levels suggest metastatic spread in medullary thyroid carcinoma (MTC) after thyroidectomy. In limited disease stages, however, morphological investigations including ultrasound, magnetic resonance imaging (MRI) and 18F-FDG positron emission tomography ([18F]FDG-PET) may often fail to identify exact tumour sites. OBJECTIVE: The aim of the present study was to establish an improved strategy to identify small cervical tumours by combining pentagastrin stimulation with bilateral cervical intravenous CT sampling followed by high-resolution ultrasound. DESIGN AND PATIENTS: Six MTC patients were examined, of whom five patients already had bilateral neck dissection. Five patients had sporadic MTC, and one patient suffered from MEN2a. RESULTS: Retrospective analysis of all patients revealed a highly sensitive positive correlation between an early calcitonin peak (20â40 s after pentagastrin injection) and site of cervical tumour affection. Postinterventional ultrasound examination of the affected regions of the neck revealed suspicious presence; in some cases small lymph nodes of less than 1 cm in size were then surgically excised. On histology, small tumours could be identified in four patients. Postsurgical examination revealed a clear decline of basal serum calcitonin levels in four patients (between â41% and â100%). In two patients CT normalized to baseline levels (< 10 pg/ml) and in another two patients CT rendered to near normal (14 and 17 pg/ml). CONCLUSION: Pentagastrin stimulation-based intravenous catheter sampling may be beneficial in the diagnostic work-up of MTC after thyroidectomy. Our data show that an early calcitonin peak (20â40 s after administration of pentagastrin) helps to identify tumour-affected regions
Flavors in the microscopic approach to N=1 gauge theories
In this note, we solve an extended version of the N=1 super Yang-Mills theory
with gauge group U(N), an adjoint chiral multiplet and Nf flavors of quarks, by
using the N=1 microscopic formalism based on Nekrasov's sums over colored
partitions. Our main new result is the computation of the general mesonic
operators. We prove that the generalized Konishi anomaly equations with flavors
are satisfied at the non-perturbative level. This yields in particular a
microscopic, first principle derivation of the matrix model disk diagram
contributions that must be included in the Dijkgraaf-Vafa approach.Comment: 20 pages, 1 figure; v2: typos corrected, refs adde
Energy-level statistics at the metal-insulator transition in anisotropic systems
We study the three-dimensional Anderson model of localization with
anisotropic hopping, i.e. weakly coupled chains and weakly coupled planes. In
our extensive numerical study we identify and characterize the metal-insulator
transition using energy-level statistics. The values of the critical disorder
are consistent with results of previous studies, including the
transfer-matrix method and multifractal analysis of the wave functions.
decreases from its isotropic value with a power law as a function of
anisotropy. Using high accuracy data for large system sizes we estimate the
critical exponent . This is in agreement with its value in the
isotropic case and in other models of the orthogonal universality class. The
critical level statistics which is independent of the system size at the
transition changes from its isotropic form towards the Poisson statistics with
increasing anisotropy.Comment: 22 pages, including 8 figures, revtex few typos corrected, added
journal referenc
Utility of TERT Promoter Mutations for Cutaneous Primary Melanoma Diagnosis
Telomerase reverse transcriptase (TERT) promoter mutations are commonly found in malignant melanomas but rare in melanocytic nevi. To assess its potential diagnostic utility for the distinction of melanoma from nevus, we determined the TERT promoter mutation status of 86 primary melanomas, 72 melanocytic nevi, and 40 diagnostically problematic melanocytic proliferations. Of the 86 melanomas, 67 (77.9%) were TERT-positive, defined as harboring a hotspot TERT promoter mutation at positions -124C>T, -124_125CC>TT, -138_139CC>TT, or -146C>T. Of the 72 nevi, only 1 (1.4%) was TERT-positive. Of the 40 diagnostically uncertain melanocytic proliferations, 2 (5.0%) were TERT-positive. TERT positivity as a test for melanoma versus nevus had an accuracy of 87.3% [95% confidence interval (CI), 81.1-92.1], a sensitivity of 77.9% (95% CI, 68.9-85.4), a specificity of 98.6% (95% CI, 95.8-100), a positive predictive value of 98.5% (95% CI, 95.6-100), and a negative predictive value of 78.9% (95% CI, 72.6-85.4). Our results indicate that hotspot TERT promoter mutation status may be a useful ancillary parameter for the diagnosis of melanoma. In particular, the high specificity of these mutations for melanoma indicates the presence of a TERT promoter mutation in a melanocytic neoplasm associated with diagnostic controversy, or uncertainty should increase concern for a melanoma
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