2,516 research outputs found
Lattice-Renormalization of the Polyakov Loop
No full textZantow F. Lattice-Renormalization of the Polyakov Loop. Bielefeld: Fakultät für Physik; 2003
GL(1) charged states in twistor string theory
No full textWe discuss the appearance of the GL(1) charged physical operators in the twistor string theory. These operators are shown to be BRST-invariant and non-trivial and some of their correlators and conformal β-functions are computed. Remarkably, the non-conservation of the GL(1) charge in interactions involving these operators, is related to the anomalous term in the Kac-Moody current algebra. While these operators play no role in the maximum helicity violating (MHV) amplitudes, they are shown to contribute non-trivially to the non-MHV correlators in the presence of the worldsheet instantons. We argue that these operators describe the non-perturbative dynamics of solitons in conformal supergravity. The exact form of such solitonic solutions is yet to be determined. © 2005 Published by Elsevier B.V.Azcarraga J., 1989, PHYS REV LETT, V3, P2443; Berkovits N., 2004, JHEP, V0404; Berkovits N., 2004, JHEP, V0408, P009; CACHAZO F, 2004, JHEP, V410; Gubser SS, 1998, PHYS LETT B, V428, P105, DOI 10.1016-S0370-2693(98)00377-3; Maldacena J M, 1998, ADV THEOR MATH PHYS, V2, P231, DOI DOI 10.1023-A:1026654312961; POLYAKOV D, HEPTH0406079; POLYAKOV D, IN PRESS INT J MOD P; Witten E., 1998, ADV THEOR MATH PHYS, V2, P253, DOI DOI 10.1016-S0370-1573(99)00083-6; Witten E., HEPTH9112056; Witten E, 2004, COMMUN MATH PHYS, V252, P189, DOI 10.1007-s00220-004-1187-344
New superstring isometries and hidden dimensions
No full textWe study the hierarchy of hidden space-time symmetries of noncritical strings in RNS formalism, realized nonlinearly. Under these symmetry transformations the variation of the matter part of the RNS action is canceled by that of the ghost part. These symmetries, referred to as the α-symmetries, are induced by special space-time generators, violating the equivalence of ghost pictures. We classify the α-symmetry generators in terms of superconformal ghost cohomologies Hn ∼ H -n-2(n andgt; 0) and associate these generators with a chain of hidden space-time dimensions, with each ghost cohomology Hn ∼ H -n-2 contributing an extra dimension. Namely, we show that each ghost cohomology Hn ∼ H-n-2 of noncritical superstring theory in d-dimensions contains d + n + 1 α-symmetry generators and the generators from Hk ∼ H-k-2, 1 andlt; k andlt; n, combined together, extend the space-time isometry group from the naive SO(d, 2) to SO(d + n, 2). In the simplest case of n = 1 the α-generators are identified with the extra symmetries of the 2T-physics formalism, also known to originate from a hidden space-time dimension. © World Scientific Publishing Company.Bars I, 1999, PHYS REV D, V59, DOI 10.1103-PhysRevD.59.045019; Bars I, 1999, PHYS REV D, V59, DOI 10.1103-PhysRevD.59.125004; Bars I, 1999, PHYS LETT B, V457, P275, DOI 10.1016-S0370-2693(99)00582-1; Bars I, 1997, PHYS REV D, V55, P2373, DOI 10.1103-PhysRevD.55.2373; KLEBANOV IR, 1991, MOD PHYS LETT A, V6, P3273, DOI 10.1142-S021773239100378X; KLEBANOV IR, 1993, PHYS REV LETT, V71, P3243, DOI 10.1103-PhysRevLett.71.3243; LIAN BH, 1991, PHYS LETT B, V254, P417, DOI 10.1016-0370-2693(91)91177-W; Polyakov D, 2007, INT J MOD PHYS A, V22, P1375, DOI 10.1142-S0217751X07035148; Polyakov D, 2007, INT J MOD PHYS A, V22, P2441, DOI 10.1142-S0217751X07036269; Vafa C, 1996, NUCL PHYS B, V469, P403, DOI 10.1016-0550-3213(96)00172-1; WITTEN E, 1992, NUCL PHYS B, V373, P187, DOI 10.1016-0550-3213(92)90454-J44
CONFORMAL MODULI AND b-c PICTURES FOR NSR STRINGS
No full textWe explore the geometry of superconformal moduli of the NSR superstring theory in order to construct the consistent sigma-model for NSR strings, free of picture-changing complications. The sigma-model generating functional is constructed by the integration over the bosonic and fermionic moduli, corresponding to insertions of the vertex operators in scattering amplitudes. While the integration over the supermoduli leads to the standard picture-changing insertions, the integration over the bosonic moduli results in the appearance of picture-changing operators for the b-c fermionic ghosts with the ghost number -1. Important example of the b-c ghost pictures involves the vertex operators in integrated and unintegrated forms. We obtain the BRST-invariant expressions for the b-c picture-changing operators for open and closed strings and study some of their properties. We also show that the superconformal moduli spaces of the NSR theory contain the global singularities, leading to the phenomenon of ghost-matter mixing and the appearance of nonperturbative D-brane creation operators. © World Scientific Publishing Company.FRADKIN ES, 1985, NUCL PHYS B, V261, P1, DOI 10.1016-0550-3213(85)90559-0; FRIEDAN D, 1986, NUCL PHYS B, V271, P93; Gubser SS, 1998, PHYS LETT B, V428, P105, DOI 10.1016-S0370-2693(98)00377-3; KNIZHNIK VG, 1989, USP FIZ NAUK+, V159, P401, DOI 10.3367-UFNr.0159.198911a.0401; KOBA Z, 1969, NUCL PHYS B, VB 12, P517, DOI 10.1016-0550-3213(69)90071-6; Kogan II, 2003, INT J MOD PHYS A, V18, P1827, DOI 10.1142-S0217751X03013715; Maldacena J M, 1998, ADV THEOR MATH PHYS, V2, P231, DOI DOI 10.1023-A:1026654312961; OHTA N, 1986, PHYS REV D, V33, P1681, DOI 10.1103-PhysRevD.33.1681; OHTA N, 1986, PHYS LETT B, V179, P349; Polchinski J, 1995, PHYS REV LETT, V75, P4724, DOI 10.1103-PhysRevLett.75.4724; Polyakov D, 2002, PHYS REV D, V65, DOI 10.1103-PhysRevD.65.084041; VERLINDE E, 1987, PHYS LETT B, V192, P95, DOI 10.1016-0370-2693(87)91148-8; Witten E., 1998, ADV THEOR MATH PHYS, V2, P253, DOI DOI 10.1016-S0370-1573(99)00083-688
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Duality and the Polyakov N-point Green's function
No full textRecently Polyakov proposed an N-point Green's function G(p/sub 1/,...,p/sub N/) for closed strings. We consider the problem of finding poles in the external momenta and extracting on-shell scattering amplitudes from G. Moreover, we find that G is invariant under complex Moebius transformations, and is presumably dual
Sensitivity of the Polyakov loop to chiral symmetry restoration
No full textClarke D, Kaczmarek O, Lahiri A, Sarkar M. Sensitivity of the Polyakov loop to chiral symmetry restoration. In: arXiv:2010.15825. 2020.In the heavy, static quark mass regime of QCD, the Polyakov loop is well known to be an order parameter of the deconfinement phase transition; however, the sensitivity of the Polyakov loop to the deconfinement of light, dynamical quarks is less clear. On the other hand, from the perspective of an effective Lagrangian written in the vicinity of the chiral transition, the Polyakov loop is an energy-like operator and should hence scale as any energy-like operator would. We show here that the Polyakov loop and heavy-quark free energy are sensitive to the chiral transition, i.e. their scaling is consistent with energy-like observables in 3-ddd O(N)O(N)O(N) universality classes
Geração radiativa de repulsão vetorial para quarks leves
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-Graduação em Física, Florianópolis, 2014Abstract: We apply a non-perturbative analytical method, known as the Optimized PerturbationTheory (OPT), to the Polyakov-Nambu-Jona-Lasinio (PNJL) model in order to investigate physical quantities associated with the QCD phase transitions. We consider the Taylor expansion of the pressure in powers of µ/T obtaining the second cumulant (c2) which is associated to the quark number susceptibility. We discuss how the OPT nite Nc radiative (quantum) corrections induce a contribution to the pressure which behaves as a vector repulsion even when such a channel is absent in the original classical potential. Our results are then compared with the ones furnished by lattice QCD simulations and by the large-Nc approximation showing that, physically, the OPT results resemble those furnished by the latter approximation when a repulsive vector channel is explicitly included in the classical potential. In this case, both approximations fail to correctly describe the Stefan-Boltzmann limit at high temperatures. We discuss how this problem can be circumvented by taking the couplings to be temperature dependent so as to simulate the phenomenon of asymptotic freedom. Since this is the first time the OPT is applied to the PNJL we also discuss many technicalities associated with the evaluation of two loop (exchange) diagrams.Neste trabalho o método analítico não perturbativo conhecido como Teoria de Perturbação Otimizada (OPT) é aplicada ao modelo de Polyakov-Nambu-Jona-Lasinio (PNJL) para que quantidades físicas, associadas com as transições de fase da QCD, possam ser calculadas. A expansão da pressão em potências de µ/T é considerada para obter o segundo cumulante (c2) que é uma quantidade relacionada com a susceptibilidade do número de quarks. Primeiramente discutimos como as correções radiativas de Nc finito geradas pela OPT produzem uma contribuição que se comporta como um termo vetorial repulsivo mesmo quando este tipo de canal está ausente no potencial clássico original. Em seguida, nossos resultados são comparados com aqueles fornecidos pelas simulações na rede e também pela aproximação de Nc grande(LN). Fisicamente, os resultados da OPT são similares aqueles fornecidos pela aproximação LN quando um canal vetorial repulsivo é explicitamente incluido no potencial clássico. Neste caso, nenhuma destas aproximações analíticas produz corretamente o limite de Stefan Boltzmann para altas temperaturas. Contudo, nossos resultados sugerem como estes problemas podem ser contornados tomando-se as constantes de acoplamento como sendo dependentes da temperatura, de maneira que o fenômeno da liberdade assimptótica possa ser simulado. Esta é a primeira vez que a OPT é aplicada ao modelo de PNJL e por isto vários aspectos técnicos relacionados com o cálculo de diagramas de dois laços são também aqui apresentados
't Hooft-Polyakov monopoles in lattice SU(N)+ adjoint Higgs theory
No full textWe investigate twisted C-periodic boundary conditions in SU(N) gauge field theory with an adjoint Higgs field. We show that with a suitable twist for even N one can impose a nonzero magnetic charge relative to residual U(1) gauge groups in the broken phase, thereby creating a ’t Hooft-Polyakov magnetic monopole. This makes it possible to use lattice Monte Carlo simulations to study the properties of these monopoles in the quantum theory.S. Edwards, D. Mehta, A. Rajantie, and L. von Smeka
A large-D Weyl invariant string model in anti-de sitter space
No full textIn this thesis we present a novel scheme for calculating the bosonic string partition function on certain curved backgrounds related to Anti-de Sitter [AdS] space. We take the concept of a large expansion from nonlinear sigma models in particle physics and apply it to the bosonic string theory sigma model, where the analogous large dimensionless parameter is the dimension of the target space, D. We then perform a perturbative expansion in negative powers of D, rather than in positive powers of α/ι(^2)(the conventional expansion parameter).As a specific example of a curved geometry of interest, we focus on an example of the metric proposed by Polyakov [1] to describe the dynamics of the Wilson loop of pure SU(N) Yang-Mills theory, namely AdS space. Using heat kernel methods, we find that within the large-D scheme one can obtain different conditions for Weyl invariance than those found in [2]. This is because our scheme is valid for backgrounds where a is no longer small. In particular, we find that it is possible to have a dilaton that depends on the holographic coordinate only, provided one allows mixing of the ghost and matter sectors of the worldsheet theory. This field preserves Poincare invariance in the gauge theory, unlike the conventional dilaton. We also compute a simple string amplitude by constructing certain vertex operators for a scalar field in AdS, and discuss the consequences for the string spectrum
Dilepton and photon production in the presence of a nontrivial Polyakov loop
No full textWe calculate the production of dileptons and photons in the presence of a nontrivial Polyakov loop in QCD. This is applicable to the semi-Quark Gluon Plasma (QGP), at temperatures above but near the critical temperature for deconfinement. The Polyakov loop is small in the semi-QGP, and near unity in the perturbative QGP. Working to leading order in the coupling constant of QCD, we find that there is a mild enhancement, ~ 20%, for dilepton production in the semi-QGP over that in the perturbative QGP. In contrast, we find that photon production is strongly suppressed in the semi-QGP, by about an order of
magnitude, relative to the perturbative QGP. In the perturbative QGP photon production contains contributions from 2->2 scattering and collinear emission with the Landau- Pomeranchuk-Migdal (LPM) effect. In the semi-QGP we show that the two contributions are modified differently. The rate for 2->2 scattering is suppressed by a factor which depends upon the Polyakov loop. In contrast, in an SU(N) gauge theory the collinear rate is suppressed by 1/N, so that the LPM effect vanishes at infinite N. To leading order in the semi-QGP at large N, we compute the rate from 2->2 scattering to the leading logarithmic order and the collinear rate to leading order
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