1,720,973 research outputs found
Stable vs. unstable vortices in SQCD
No full textWe give a topological classification of stable and unconfined massive particles and strings (and some instantons) in worldvolume theories of M5-branes and their dimensional reductions, generalizing Witten's classification of strings in SYM. In particular 4d = 2 SQCD softly broken to = 1 contains torsion (Douglas-Shenker) N-strings and nontorsion (Hanany-Tong) -strings. Some of the former are stable when the flavor symmetry is gauged, while those that are not stable confine quarks and in some vacua even dyons into baryons. The nontorsion strings are stable if and only if all colors are locked to flavors, which is weaker than the BPS condition. As a byproduct unstable string decay modes and approximate lifetimes are found. Cascading theories have no vortices stabilized by the topological charges treated here and in particular Gubser-Herzog-Klebanov axionic strings do not carry such a charge. © SISSA 2006.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Monopoles can be confined by 0, 1 or 2 vortices
No full textThere are three types of monopole in gauge theories with fundamental matter and N = 2 supersymmetry broken by a superpotential. There are unconfined 0-monopoles and also 1 and 2-monopoles confined respectively by one or two vortices transforming under distinct components of the unbroken gauge group. If a Fayet-Iliopoulos term is added then there are only 2-monopoles. Monopoles transform in the bifundamental representation of two components of the unbroken gauge symmetry, and if two monopoles share a component they may form a boundstate. Selection rules for this process are found, for example vortex number is preserved modulo 2. We find the tensions of the vortices, which are in general distinct, and also the conditions under which vortices are mutually BPS. Results are derived in field theory and also in MQCD, and in quiver theories a T-dual picture may be used in which monopoles are classified by quiver diagrams with two colors of vertices. © SISSA/ISAS 2005.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Nonabelian Monopoles and the Vortices that Confine Them
No full textNonabelian magnetic monopoles of Goddard-Nuyts-Olive-Weinberg type have
recently been shown to appear as the dominant infrared degrees of freedom in a
class of softly broken supersymmetric gauge theories in which the
gauge group is broken to various nonabelian subgroups by an adjoint
Higgs VEV. When the low-energy gauge group is further broken completely by
e.g. squark VEVs, the monopoles representing are confined by the
nonabelian vortices arising from the breaking of , discussed recently
(hep-th/0307278). By considering the system with , H = {SU(N)
\times U(1) {\o}{\mathbb Z}_N}, as an example, we show that the total magnetic
flux of the minimal monopole agrees precisely with the total magnetic flux
flowing along the single minimal vortex.
The possibility for such an analysis reflects the presence of free parameters
in the theory - the bare quark mass and the adjoint mass - such that
for the topologically nontrivial solutions of vortices and of
unconfined monopoles exist at distinct energy scales
On Holographic Superconductors with DC Current
Full text linkWe study direct currents in a simple holographic realization of a superconducting film. We investigate how the presence of a DC current affects the superconducting phase transition, which becomes first order for any non-vanishing value of the current, as well as several other properties of the superconductor such as the AC conductivity. Near the critical temperature we find a quantitative agreement with several properties of Ginzburg-Landau superconducting films, for example the squared ratio of the maximal and minimal condensate is equal to two thirds. We also comment on the extension of our construction to holographic Josephson junctions
Nonabelian Superconductors: Vortices and Confinement in SQCD
No full textWe study nonabelian vortices (flux tubes) in SU(N) gauge theories, which are
responsible for the confinement of (nonabelian) magnetic monopoles. In
particular a detailed analysis is given of SQCD with gauge group
SU(3) deformed by a small adjoint chiral multiplet mass. Tuning the bare quark
masses (which we take to be large) to a common value , we consider a
particular vacuum of this theory in which an SU(2) subgroup of the gauge group
remains unbroken. We consider flavors so that the SU(2)
sub-sector remains non asymptotically free: the vortices carrying nonabelian
fluxes may be reliably studied in a semi-classical regime. We show that the
vortices indeed acquire exact zero modes which generate global rotations of the
flux in an group. We study an effective world-sheet theory of
these orientational zero modes which reduces to an O(3) sigma
model in (1+1) dimensions. Mirror symmetry then teaches us that the dual SU(2)
group is not dynamically broken
Measuring θ12 despite an uncertain reactor neutrino spectrum
No full textAbstractThe recently discovered 5–7 MeV excess in the reactor neutrino spectral structure, corresponding to a prompt energy of 4–6 MeV, highlights that the uncertainty in the reactor neutrino spectrum is far greater than some theoretical estimates. Medium baseline (about 50 km) reactor neutrino experiments will deliver by far the most precise ever measurements of θ12. However, the theoretical reactor neutrino spectra, as they were recalculated in 2011, do not reproduce this excess. As a result, if a medium baseline experiment attempted to determine sin2(2θ12) using the theoretical spectrum, the result would have a systematic upward bias of 1%, much larger than the expected uncertainty. We show that by using recent measurements of the reactor neutrino spectrum the precision of a measurement of θ12 at a medium baseline reactor neutrino experiment can be improved appreciably. We estimate this precision as a function of the 9Li spallation background veto efficiency and dead time
Nonabelian Faddeev-Niemi Decomposition of the SU(3) Yang-Mills Theory
No full textFaddeev and Niemi (FN) have introduced an abelian gauge theory which
simulates dynamical abelianization in Yang-Mills theory (YM). It contains both
YM instantons and Wu-Yang monopoles and appears to be able to describe the
confining phase. Motivated by the meson degeneracy problem in dynamical
abelianization models, in this note we present a generalization of the FN
theory. We first generalize the Cho connection to dynamical symmetry breaking
pattern SU(N+1) -> U(N), and subsequently try to complete the Faddeev-Niemi
decomposition by keeping the missing degrees of freedom. While it is not
possible to write an on-shell complete FN decomposition, in the case of SU(3)
theory of physical interest we find an off-shell complete decomposition for
SU(3) -> U(2) which amounts to partial gauge fixing, generalizing naturally the
result found by Faddeev and Niemi for the abelian scenario SU(N+1) -> U(1)^N.
We discuss general topological aspects of these breakings, demonstrating for
example that the FN knot solitons never exist when the unbroken gauge symmetry
is nonabelian, and recovering the usual no-go theorems for colored dyons
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
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