22 research outputs found
Yang-Mills Correlation Functions from Integrable Spin Chains
The relation between the dilatation operator of N=4 Yang-Mills theory and
integrable spin chains makes it possible to compute the one-loop anomalous
dimensions of all operators in the theory. In this paper we show how to apply
the technology of integrable spin chains to the calculation of Yang-Mills
correlation functions by expressing them in terms of matrix elements of spin
operators on the corresponding spin chain. We illustrate this method with
several examples in the SU(2) sector described by the XXX_1/2 chain.Comment: 27 pages, 3 figures, harvma
Semiclassical Strings on AdS_5 x S^5/Z_M and Operators in Orbifold Field Theories
We show agreements, at one-loop level of field theory, between energies of
semiclassical string states on AdS_5 x S^5/Z_M and anomalous dimensions of
operators in N=0,1,2 orbifold field theories originating from N=4 SYM. On field
theory side, one-loop anomalous dimension matrices can be regarded as
Hamiltonians of spin chains with twisted boundary conditions. These are
solvable by Bethe ansatz. On string side, twisted sectors emerge and we obtain
some string configurations in twisted sectors. In SU(2) subsectors, we compare
anomalous dimensions with string energies and see agreements. We also see
agreements between sigma models of both sides in SU(2) and SU(3) subsectors.Comment: LaTeX, 23 pages, 4 figures; v2 minor corrections, added references;
v3 typos corrected, published versio
Circular and Folded Multi-Spin Strings in Spin Chain Sigma Models
From the SU(2) spin chain sigma model at the one-loop and two-loop orders we
recover the classical circular string solution with two S^5 spins (J_1, J_2) in
the AdS_5 x S^5 string theory. In the SL(2) sector of the one-loop spin chain
sigma model we explicitly construct a solution which corresponds to the folded
string solution with one AdS_5 spin S and one S^5 spin J. In the one-loop
general sigma model we demonstrate that there exists a solution which
reproduces the energy of the circular constant-radii string solution with three
spins (S_1, S_2, J).Comment: 16 pages, LaTeX, no figure
A Novel Long Range Spin Chain and Planar N=4 Super Yang-Mills
We probe the long-range spin chain approach to planar N=4 gauge theory at
high loop order. A recently employed hyperbolic spin chain invented by
Inozemtsev is suitable for the SU(2) subsector of the state space up to three
loops, but ceases to exhibit the conjectured thermodynamic scaling properties
at higher orders. We indicate how this may be bypassed while nevertheless
preserving integrability, and suggest the corresponding all-loop asymptotic
Bethe ansatz. We also propose the local part of the all-loop gauge transfer
matrix, leading to conjectures for the asymptotically exact formulae for all
local commuting charges. The ansatz is finally shown to be related to a
standard inhomogeneous spin chain. A comparison of our ansatz to semi-classical
string theory uncovers a detailed, non-perturbative agreement between the
corresponding expressions for the infinite tower of local charge densities.
However, the respective Bethe equations differ slightly, and we end by refining
and elaborating a previously proposed possible explanation for this
disagreement.Comment: 48 pages, 1 figure. v2, further results added: discussion of the
relationship to an inhomogeneous spin chain, normalization in sec 3 unified,
v3: minor mistakes corrected, published versio
Classical/quantum integrability in non-compact sector of AdS/CFT
We discuss non-compact SL(2,R) sectors in N=4 SYM and in AdS string theory
and compare their integrable structures. We formulate and solve the
Riemann-Hilbert problem for the finite gap solutions of the classical sigma
model and show that at one loop it is identical to the classical limit of Bethe
equations of the spin (-1/2) chain for the dilatation operator of SYM.Comment: 27 pages, 1 figure; v2: unphysical windings around the time direction
eliminated; v3: dicsussion of finite-size corrections remove
Finite-Size Corrections to Anomalous Dimensions in N=4 SYM Theory
The scaling dimensions of large operators in N=4 supersymmetric Yang-Mills
theory are dual to energies of semiclassical strings in AdS(5)xS(5). At one
loop, the dimensions of large operators can be computed with the help of Bethe
ansatz and can be directly compared to the string energies. We study
finite-size corrections for Bethe states which should describe quantum
corrections to energies of extended semiclassical strings.Comment: 10 page
Co-evolution, opportunity seeking and institutional change: Entrepreneurship and the Indian telecommunications industry 1923-2009
"This is an Author's Original Manuscript of an article submitted for consideration in Business History [copyright Taylor & Francis]; Business History is available online at http://www.tandfonline.com/." 10.1080/00076791.2012.687538In this paper, we demonstrate the importance for entrepreneurship of historical contexts and processes, and the co-evolution of institutions, practices, discourses and cultural norms. Drawing on discourse and institutional theories, we develop a model of the entrepreneurial field, and apply this in analysing the rise to global prominence of the Indian telecommunications industry. We draw on entrepreneurial life histories to show how various discourses and discursive processes ultimately worked to generate change and the creation of new business opportunities. We propose that entrepreneurship involves more than individual acts of business creation, but also implies collective endeavours to shape the future direction of the entrepreneurial field
Feasibility of a New Wearable Device to Estimate Acute Stress in Novices During High-fidelity Surgical Simulation
BACKGROUND: Stress associated with learning of a psychomotor task can influence the trainees learning ability. Surgical simulation is a validated training milieu designed to replicate real-life situations, prevent biases and provide objective metrics. However, the complexity of stress mechanisms and the absence of a reliable detection method make stress estimation difficult to quantify and to interpret. AIM: a) To assess the feasibility of a new watch-sized device to noninvasively measure stress parameters in novices during a simulation task and b) to compare its derived cardiac stress parameters to those of an ambulatory Holter monitor. MATERIALS AND METHODS: Twenty-one novices were trained on a basic skills module. During base line, exercise, and recovery phases, all subjects wore a wearable device and data regarding blood volume pressure, heart rate, inter beat interval, electrodermal activity, and skin temperature were recorded. Additionally, Holter Monitoring was used to concomitantly capture heart rate, R-R intervals and heart rate variability. Before and after each experiment, all subjects completed the short, six-item STAI scale. RESULTS: Data analysis showed: a) when compared to STAI, electrodermal activity exhibited the best correlation, sensitivity and specificity and b) the device derived cardiac parameters highly correlated with the reciprocal Holter values during all experiment phases. CONCLUSION: This wearable device is an easy to use and well accepted by the participants noninvasive tool, which can provide accurate stress estimation in our simulation setting. Additionally, it can replicate Holter derived stress related heart parameters, thus eliminating the need to wear a rather cumbersome device
Mathematical and experimental simulation of a cylindrical plasma target trap with inverse magnetic mirrors
A plasma target for highly efficient neutralization of powerful negative ion beams is considered. The plasma is confined within a magnetic trap with multipole magnetic walls. It is proposed to use inverse magnetic mirrors to limit plasma outflow through the inlet and outlet holes in the trap. Using the particle-in-cell method, mathematical simulation of plasma dynamics in the trap has been performed. The estimates of plasma distribution and particle confinement efficiency in the region of the magnetic mirrors has been obtained. Simulation results were compared with experimental data