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Search Results: 1 - 10 of 19 matches for " Iouri; "
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Are M-atrix theory and Maldacena's conjecture related?
Iouri Chepelev
Physics , 1999, DOI: 10.1016/S0370-2693(99)00362-7
Abstract: We give arguments in the support of a relation between M-atrix theory and Maldacena's conjecture. M-atrix theory conjecture implies the equivalence of 11-D light-cone supergravity and strongly-coupled (0+1)-D SYM. Maldacena's SUGRA/SYM duality conjecture implies, in the one dimensional SYM case, the equivalence between strongly-coupled (0+1)-D SYM and 11-D supergravity compactified on a spatial circle in the formal Seiberg-Sen limit. Using the classical equivalence between 11-D supergravity on a light-like circle and on a spatial circle in the formal Seiberg-Sen limit, we argue that in the (0+1)-D SYM case, the large-N M-atrix theory in the supergravity regime is equivalent to SUGRA/SYM duality.
Non-Abelian Wilson Surfaces
Iouri Chepelev
Physics , 2001, DOI: 10.1088/1126-6708/2002/02/013
Abstract: A definition of non-abelian genus zero open Wilson surfaces is proposed. The ambiguity in surface-ordering is compensated by the gauge transformations.
Supersymmetric Matrix Models and the Meander Problem
Yuri Makeenko,Iouri Chepelev
Physics , 1996,
Abstract: We consider matrix-model representations of the meander problem which describes, in particular, combinatorics for foldings of closed polymer chains. We introduce a supersymmetric matrix model for describing the principal meander numbers. This model is of the type proposed by Marinari and Parisi for discretizing a superstring in D=1 while the supersymmetry is realized in D=0 as a rotational symmetry between bosonic and fermionic matrices. Using non-commutative sources, we reformulate the meander problem in a Boltzmannian Fock space whose annihilation and creation operators obey the Cuntz algebra. We discuss also the relation between the matrix models describing the meander problem and the Kazakov-Migdal model on a D-dimensional lattice.
A Path Integral Approach To Noncommutative Superspace
Iouri Chepelev,Calin Ciocarlie
Physics , 2003, DOI: 10.1088/1126-6708/2003/06/031
Abstract: A path integral formula for the associative star-product of two superfields is proposed. It is a generalization of the Kontsevich-Cattaneo-Felder's formula for the star-product of functions of bosonic coordinates. The associativity of the star-product imposes certain conditions on the background of our sigma model. For generic background the action is not supersymmetric. The supersymmetry invariance of the action constrains the background and leads to a simple formula for the star-product.
K0s and Λ production in Pb--Pb collisions with the ALICE experiment
Iouri Belikov,for the ALICE Collaboration
Physics , 2011, DOI: 10.1088/0954-3899/38/12/124078
Abstract: We present the study of K0s and Lambda production performed with the ALICE experiment at the LHC in Pb--Pb collisions at \sqrt{s_NN}=2.76 TeV and pp collisions at \sqrt{s}=0.9 and 7 TeV. The K0s and Lambda particles are reconstructed via their V0 decay topology allowing their identification up to high transverse momenta. The corresponding baryon/meson ratios as a function of transverse momentum are extracted for Pb--Pb collisions in centrality bins and in the transverse momentum range from 1 to 6 GeV/c. They are also compared with those measured in pp events at the LHC energies of 0.9 and 7 TeV as well as in Au--Au collisions at \sqrt{s_NN} = 62.4 and 200 GeV from RHIC.
Convergence Theorem for Non-commutative Feynman Graphs and Renormalization
Iouri Chepelev,Radu Roiban
Physics , 2000, DOI: 10.1088/1126-6708/2001/03/001
Abstract: We present a rigorous proof of the convergence theorem for the Feynman graphs in arbitrary massive Euclidean quantum field theories on non-commutative R^d (NQFT). We give a detailed classification of divergent graphs in some massive NQFT and demonstrate the renormalizability of some of these theories.
A note on correlation functions in AdS_5/SYM_4 correspondence on the Coulomb branch
Iouri Chepelev,Radu Roiban
Physics , 1999, DOI: 10.1016/S0370-2693(99)00886-2
Abstract: We compute certain two-point functions in D=4, ${\cal N}=4$, SU(N) SYM theory on the Coulomb branch using SUGRA/SYM duality and find an infinite set of first order poles at masses of order $({\rm Higgs~scale})/(g_{YM} \sqrt{N})$.
Renormalization of Quantum Field Theories on Noncommutative R^d, I. Scalars
Iouri Chepelev,Radu Roiban
Physics , 1999, DOI: 10.1088/1126-6708/2000/05/037
Abstract: A noncommutative Feynman graph is a ribbon graph and can be drawn on a genus $g$ 2-surface with a boundary. We formulate a general convergence theorem for the noncommutative Feynman graphs in topological terms and prove it for some classes of diagrams in the scalar field theories. We propose a noncommutative analog of Bogoliubov-Parasiuk's recursive subtraction formula and show that the subtracted graphs from a class $\Omega_d$ satisfy the conditions of the convergence theorem. For a generic scalar noncommutative quantum field theory on $\re^d$, the class $\Omega_d$ is smaller than the class of all diagrams in the theory. This leaves open the question of perturbative renormalizability of noncommutative field theories. We comment on how the supersymmetry can improve the situation and suggest that a noncommutative analog of Wess-Zumino model is renormalizable.
Criterion for linear independence of functions
Iouri V. Romanovski
Mathematics , 2009,
Abstract: Using a generalization of forward elimination, it is proved that functions $f_1,...,f_n:X\to\mathbb{A}$, where $\mathbb{A}$ is a field, are linearly independent if and only if there exists a nonsingular matrix $[f_i(x_j)]$ of size $n$, where $x_1,...,x_n\in X$.
Prediction of regulatory elements in mammalian genomes using chromatin signatures
Kyoung-Jae Won, Iouri Chepelev, Bing Ren, Wei Wang
BMC Bioinformatics , 2008, DOI: 10.1186/1471-2105-9-547
Abstract: We present here a supervised learning method to predict promoters and enhancers based on their unique chromatin modification signatures. We trained Hidden Markov models (HMMs) on the histone modification data for known promoters and enhancers, and then used the trained HMMs to identify promoter or enhancer like sequences in the human genome. Using a simulated annealing (SA) procedure, we searched for the most informative combination and the optimal window size of histone marks.Compared with the previous methods, the HMM method can capture the complex patterns of histone modifications particularly from the weak signals. Cross validation and scanning the ENCODE regions showed that our method outperforms the previous profile-based method in mapping promoters and enhancers. We also showed that including more histone marks can further boost the performance of our method. This observation suggests that the HMM is robust and is capable of integrating information from multiple histone marks. To further demonstrate the usefulness of our method, we applied it to analyzing genome wide ChIP-Seq data in three mouse cell lines and correctly predicted active and inactive promoters with positive predictive values of more than 80%. The software is available at http://http:/nash.ucsd.edu/chromatin.tar.gz webcite.Transcriptional regulation in eukaryotic cells requires highly orchestrated interactions between transcription factors (TFs), their co-factors, RNA polymerase and the chromatin [1,2]. Several classes of regulatory elements, including promoters, enhancers, silencer and insulators, are involved in this process. Systematic and precise mapping of these elements in the genome is essential for understanding transcriptional programs responsible for temporal and tissue specific gene expression. A high throughput experimental approach has recently been used to tackle this problem and it involves the chromatin immunoprecipitation assay followed by microarray (ChIP-chip)[3,4] or large s
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