1,720,977 research outputs found
Flavoured large N gauge theory on a compact space with an external magnetic field
Get PDFThe phase structure of flavoured N = 2 SYM on a three sphere in an external magnetic field is studied. The pairing effect of the magnetic field competes with the dissociating effect of the Casimir energy, leading to an interesting phase structure of confined and deconfined phases separated by a critical curve of a first order quantum phase transition. At vanishing magnetic field the phase transition is of a third order. For sufficiently strong magnetic field, the only stable phase is the confined phase and magnetic catalysis of chiral symmetry breaking is realized. The meson spectra of the theory exhibit Zeeman splitting and level crossing and feature a finite jump at the phase transition between the confined and deconfined phases. At strong magnetic field the ground state has a massless mode corresponding to the Goldstone boson associated with the spontaneously broken U(1) R-symmetry analogous to the η' meson in QCD
Multi-matrix models at general coupling
Get PDFThe eigenvalue distribution of Hoppe’s two matrix model is investigated in detail as a function of the model’s coupling. For small couplings it is a perturbed Wigner semicircle, while for large couplings it is a parabolic distribution which crosses over to a Wigner semicircle for eigenvalues within approximately an inverse coupling from the boundary of the distribution. The model is approximately commuting at large couplings and we find the joint eigenvalue distribution of the two matrices. We also study a related three matrix model finding the corresponding three dimensional eigenvalue distribution there also. The techniques developed here are more widely applicable to other multi-matrix models
Near commuting multi-matrix models
Get PDFWe investigate the radial extent of the eigenvalue distribution for Yang-Mills type matrix models. We show that, a three matrix Gaussian model with complex Myers coupling, to leading order in strong coupling is described by commuting matrices whose joint eigenvalue distribution is uniform and confined to a ball of radius R = (3π/2g)^1/3 then study, perturbatively, a 3-component model with a pure commutator action and find a radial extent broadly consistent with numerical simulations
Membrane Matrix models and non-perturbative checks of gauge/gravity duality
Get PDFWe compare the bosonic and maximally supersymmetric membrane models. We find that in Hoppe regulated form the bosonic membrane is well approximated by massive Gaussian quantum matrix models. In contrast the similarly regulated supersymmetric membrane, which is equivalent to the BFSS model, has a gravity dual description. We sketch recent progress in checking gauge/gravity duality in this context
Aspects of the holographic study of flavor dynamics
Get PDFUnrestrictedThis thesis is dedicated to the holographic study of flavor dynamics. The technique employed is a D7-brane probing of various D3-brane backgrounds. The first topic covered studies the influence of an external magnetic field on a flavored large N Yang-Mills theory. The theory exhibits spontaneous chiral symmetry breaking. A discrete self-similar structure of the spontaneous symmetry breaking mechanism is observed, this structure is reflected in the meson spectrum. The meson spectrum exhibits Zeeman splitting and characteristic GMOR relation. The second topic examines thermal properties of the dual gauge theory. The study reveals a first order phase transition associated to the melting of mesons. The critical ratio of the bare quark mass and temperature at which the transition happens is computed. The third topic studies the phase structure of the finite temperature dual gauge theory in the presence of magnetic field. A phase diagram of the theory is obtained. The temperature restores the chiral symmetry while the magnetic field has a freezing effect on the meson melting. The meson spectrum exhibits Zeeman splitting and characteristic GMOR relation. Thermodynamic quantities such as free energy, entropy, and magnetization are computed.; The fourth topic studies the addition of an external electric field. The observed effect is dissociation of the bound quarks, favoring the meson melting. For sufficiently strong electric fields a global electric current is induced. Thus, the dissociation of mesons corresponds to an insulator/conductor phase transition. This transition persists at vanishing temperature. The fifth topic studies the addition of an R-charge chemical potential via brane probing of the spinning D3-brane geometry. The corresponding phase diagram is obtained. The chemical potential favors the dissociation of mesons. For high chemical potential, a finite phase difference between the bare quark mass and the quark condensate is induced. The last topic explores universal properties of gauge theories dual to the Dp/Dq system. A universal discrete self-similar behavior associated to the insulator/conductor phase transition is observed and the corresponding scaling exponents are computed. A similarity between the electric field and R-charge chemical potential cases is discussed
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
A Quantum Critical Point from Flavours on a Compact Space
Get PDFAbstract: We analyse a 2 + 1 dimensional defect field theory on a two sphere in an external magnetic field. The theory is holographically dual to probe D5-branes in global AdS5 × S5 background. At any finite magnetic field only the confined phase of the theory is realised. There is a first order quantum phase transition, within the confined phase of theory, ending on a quantum critical point of a second order phase transition. We analyse the condensate and magnetisation of theory and construct its phase diagram. We study the critical exponents near the quantum critical point and find that the second derivatives of the free energy, with respect to the bare mass and the magnetic field, diverge with a critical exponent of −2/3. Next, we analyse the meson spectrum of the theory and identify a massless mode at the critical point signalling a diverging correlation length of the quantum fluctuations. We find that the derivative of the meson mass with respect to the bare mass also diverges with a critical exponent of −2/3. Finally, our studies of the magnetisation uncover a persistent diamagnetic response similar to that in mesoscopic systems, such as quantum dots and nano tubes. ar X i
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