6,649 research outputs found
Gluon Scattering Amplitudes in Finite Temperature Gauge/Gravity Dualities
We examine the gluon scattering amplitude in N=4 super Yang-Mills at finite
temperature with nonzero R-charge densities, and in Non-Commutative gauge
theory at finite temperature. The gluon scattering amplitude is defined as a
light-like Wilson loop which lives at the horizon of the T-dual black holes of
the backgrounds we consider. We study in detail a special amplitude, which
corresponds to forward scattering of a low energy gluon off a high energy one.
For this kinematic configuration in the considered backgrounds, we find the
corresponding minimal surface which is directly related to the gluon scattering
amplitude. We find that for increasing the chemical potential or the
non-commutative parameter, the on-shell action corresponding to our Wilson loop
in the T-dual space decreases. For all of our solutions the length of the short
side of the Wilson loop is constrained by an upper bound which depends on the
temperature, the R-charge density and the non-commutative parameter. Due to
this constraint, in the limit of zeroth temperature our approach breaks down
since the upper bound goes to zero, while by keeping the temperature finite and
letting the chemical potential or the non-commutative parameter to approach to
zero the limit is smooth.Comment: 30 pages, 16 figures, minor corrections (plus improved numerical
computation for the non-commutative case
Wilson Loops in N=2 Super-Yang-Mills from Matrix Model
We compute the expectation value of the circular Wilson loop in N=2
supersymmetric Yang-Mills theory with N_f=2N hypermultiplets. Our results
indicate that the string tension in the dual string theory scales as the
logarithm of the 't Hooft coupling.Comment: 37 pages, 9 figures; v2: Numerical factors corrected, simple
derivation of Wilson loop and discussion of continuation to complex lambda
added; v3: instanton partition function re-analyzed in order to take into
account a contribution of the hypermultiplet
Glycated hemoglobin and incident type 2 diabetes in singaporean Chinese adults: The Singapore Chinese Health Study
Background: The American Diabetes Association recently included glycated hemoglobin in the diagnostic criteria for diabetes, but research on the utility of this biomarker in Southeast Asians is scant. The aim of this study was to evaluate the association between percent HbA1c and incident diabetes in an Asian population of adult men and women without reported diabetes. Methods: Data analysis of 5,770 men and women enrolled in the Singapore Chinese Health Study who provided a blood sample at the follow-up I visit (1999-2004) and had no cancer and no reported history of diabetes or cardiovascular disease events. Diabetes was defined as self-report of physician diagnosis, identified at the follow-up II visit (2006-2010). Results: Hazard ratios (and 95%confidence intervals) for incident diabetes by 5 categories of HbA1c were estimated with Cox regression models and continuous HbA1c with cubic spline analysis. Compared to individuals with an HbA1c ≤ 5.7% (≤39 mmol/mol), individuals with HbA1c 5.8-5.9% (40-41 mmol/mol), 6.0-6.1% (42-43 mmol/mol), 6.2-6.4% (44-47 mmol/mol), and ≥ 6.5% (≥48 mmol/mol) had significantly increased risk for incident diabetes during followup. In cubic spline analysis, levels below 5.7% HbA1c were not significantly associated with incident diabetes. Conclusions: Our study found a strong and graded association with HbA1c 5.8% and above with incident diabetes in Chinese men and women
Global AdS Picture of 1/2 BPS Wilson Loops
We study the holographic dual string configuration of 1/2 BPS circular Wilson
loops in N=4 super Yang-Mills theory by using the global coordinate of AdS. The
dual string worldsheet is given by the Poincare disk AdS_2 sitting at a
constant global time slice of AdS_5. We also analyze the correlator of two
concentric circular Wilson loops from the global AdS perspective and study the
phase transition associated with the instability of annulus worldsheet
connecting the two Wilson loops.Comment: 14 pages, 3 figures, v2: discussion on two branches corrected, v3:
reference adde
On semiclassical approximation for correlators of closed string vertex operators in AdS/CFT
We consider the 2-point function of string vertex operators representing
string state with large spin in AdS_5. We compute this correlator in the
semiclassical approximation and show that it has the expected (on the basis of
state-operator correspondence) form of the strong-coupling limit of the 2-point
function of single trace minimal twist operators in gauge theory. The
semiclassical solution representing the stationary point of the path integral
with two vertex operator insertions is found to be related to the large spin
limit of the folded spinning string solution by a euclidean continuation,
transformation to Poincare coordinates and conformal map from cylinder to
complex plane. The role of the source terms coming from the vertex operator
insertions is to specify the parameters of the solution in terms of quantum
numbers (dimension and spin) of the corresponding string state. Understanding
further how similar semiclassical methods may work for 3-point functions may
shed light on strong-coupling limit of the corresponding correlators in gauge
theory as was recently suggested by Janik et al in arXiv:1002.4613.Comment: 19 pages, 1 figure; minor corrections, references added, footnote
below eq. (4.5) adde
Gauge invariant perturbation theory and non-critical string models of Yang-Mills theories
We carry out a gauge invariant analysis of certain perturbations of
-branes solutions of low energy string theories. We get generically a
system of second order coupled differential equations, and show that only in
very particular cases it is possible to reduce it to just one differential
equation. Later, we apply it to a multi-parameter, generically singular family
of constant dilaton solutions of non-critical string theories in
dimensions, a generalization of that recently found in arXiv:0709.0471[hep-th].
According to arguments coming from the holographic gauge theory-gravity
correspondence, and at least in some region of the parameters space, we obtain
glue-ball spectra of Yang-Mills theories in diverse dimensions, putting special
emphasis in the scalar metric perturbations not considered previously in the
literature in the non critical setup. We compare our numerical results to those
studied previously and to lattice results, finding qualitative and in some
cases, tuning properly the parameters, quantitative agreement. These results
seem to show some kind of universality of the models, as well as an irrelevance
of the singular character of the solutions. We also develop the analysis for
the T-dual, non trivial dilaton family of solutions, showing perfect agreement
between them.Comment: A new reference added
Efficacy of an ankle orthosis with a subtalar locking system in restricting ankle kinetics and kinematics in lateral cutting
Introduction
The ankle joint is the most injured joint during sports participation [1]. Ankle orthoses have been shown to be effective in reducing ankle inversion injuries and are often prescribed for rehabilitation and prevention of lateral ankle sprains. Efficacy of ankle orthoses is often assessed by comparing reduction of passive inversion ROM as well as ankle kinematics between braced and unbraced movements [2,3]. However, joint kinetic responses in lateral cutting were rarely examined. Therefore, the objective of this study was to examine the effectiveness of a new semi-rigid ankle orthosis with a subtalar joint locking mechanism in restricting ankle kinetics and kinematics during a lateral cutting movement
From correlation functions to Wilson loops
We start with an n-point correlation function in a conformal gauge theory. We
show that a special limit produces a polygonal Wilson loop with sides. The
limit takes the points towards the vertices of a null polygonal Wilson loop
such that successive distances . This produces a fast moving
particle that generates a "frame" for the Wilson loop. We explain in detail how
the limit is approached, including some subtle effects from the propagation of
a fast moving particle in the full interacting theory. We perform perturbative
checks by doing explicit computations in N=4 super-Yang-Mills.Comment: 37 pages, 10 figures; typos corrected, references adde
Thermodynamic Properties of Holographic Multiquark and the Multiquark Star
We study thermodynamic properties of the multiquark nuclear matter. The
dependence of the equation of state on the colour charges is explored both
analytically and numerically in the limits where the baryon density is small
and large at fixed temperature between the gluon deconfinement and chiral
symmetry restoration. The gravitational stability of the hypothetical
multiquark stars are discussed using the Tolman-Oppenheimer-Volkoff equation.
Since the equations of state of the multiquarks can be well approximated by
different power laws for small and large density, the content of the multiquark
stars has the core and crust structure. We found that most of the mass of the
star comes from the crust region where the density is relatively small. The
mass limit of the multiquark star is determined as well as its relation to the
star radius. For typical energy density scale of ,
the converging mass and radius of the hypothetical multiquark star in the limit
of large central density are approximately solar mass and 15-27 km.
The adiabatic index and sound speed distributions of the multiquark matter in
the star are also calculated and discussed. The sound speed never exceeds the
speed of light and the multiquark matters are thus compressible even at high
density and pressure.Comment: 27 pages, 17 figures, 1 table, JHEP versio
Bounds for State Degeneracies in 2D Conformal Field Theory
In this note we explore the application of modular invariance in
2-dimensional CFT to derive universal bounds for quantities describing certain
state degeneracies, such as the thermodynamic entropy, or the number of
marginal operators. We show that the entropy at inverse temperature 2 pi
satisfies a universal lower bound, and we enumerate the principal obstacles to
deriving upper bounds on entropies or quantum mechanical degeneracies for fully
general CFTs. We then restrict our attention to infrared stable CFT with
moderately low central charge, in addition to the usual assumptions of modular
invariance, unitarity and discrete operator spectrum. For CFT in the range
c_left + c_right < 48 with no relevant operators, we are able to prove an upper
bound on the thermodynamic entropy at inverse temperature 2 pi. Under the same
conditions we also prove that a CFT can have a number of marginal deformations
no greater than ((c_left + c_right) / (48 - c_left - c_right)) e^(4 Pi) - 2.Comment: 23 pages, LaTeX, minor change
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