1,583 research outputs found
Whitham Deformations of Seiberg-Witten Curves for Classical Gauge Groups
Gorsky et al. presented an explicit construction of Whitham deformations of
the Seiberg-Witten curve for the \calN = 2 SUSY Yang-Mills theory.
We extend their result to all classical gauge groups and some other cases such
as the spectral curve of the affine Toda Toda system. Our
construction, too, uses fractional powers of the superpotential that
characterizes the curve. We also consider the -plane integral of
topologically twisted theories on four-dimensional manifolds with
in the language of these explicitly constructed Whitham
deformations and an integrable hierarchy of the KdV type hidden behind.Comment: latex, 39pp, no figure; some more comments and references on
integrable systems are added, and many typos are correcte
Noncommutative Riemann Surfaces
We compactify M(atrix) theory on Riemann surfaces Sigma with genus g>1.
Following [1], we construct a projective unitary representation of pi_1(Sigma)
realized on L^2(H), with H the upper half-plane. As a first step we introduce a
suitably gauged sl_2(R) algebra. Then a uniquely determined gauge connection
provides the central extension which is a 2-cocycle of the 2nd Hochschild
cohomology group. Our construction is the double-scaling limit N\to\infty,
k\to-\infty of the representation considered in the Narasimhan-Seshadri
theorem, which represents the higher-genus analog of 't Hooft's clock and shift
matrices of QCD. The concept of a noncommutative Riemann surface Sigma_\theta
is introduced as a certain C^\star-algebra. Finally we investigate the Morita
equivalence.Comment: LaTeX, 1+14 pages. Contribution to the TMR meeting ``Quantum aspects
of gauge theories, supersymmetry and unification'', Paris 1-7 September 199
A strength and serviceability assessment of high performance steel Bridge 10462
High performance steels (HPS) were developed through the cooperative efforts of the American Iron and Steel Institute (AISI), the US Navy, and the Federal Highway Administration (FHWA). They offer several advantages over conventional bridge steels including greater yield strengths, improved ductility, increased toughness, and better welding characteristics. The three grades of HPS that are currently available in today\u27s bridge market are HPS 50W, 70W, and 100W. The current steel I-girder flexural capacity equations, however, were specifically developed for girders with nominal yield strengths less than or equal to 70 ksi. Because of this fact, the flexural capacities of I-girders incorporating HPS 100W have been restricted due to a lack of experimental and/or analytical evidence that supports the applicability of existing equations. In particular, the design flexural capacities of compact and noncompact sections in negative flexure are currently limited to their yield moment capacities (My) instead of their plastic moment capacities (Mp).;The focus of this research project was to experimentally and analytically evaluate the applicability of the current design specifications for I-girders fabricated with HPS 100W. In particular, the strength and serviceability of the Culloden Railroad Overpass (WVDOH Bridge No. 10462) was assessed by conducting static and dynamic load tests. The Culloden Bridge is a three-span-continuous bridge that utilizes HPS 100W in the compression flanges of sections in negative flexure at interior supports. The experimental natural frequency, lateral live load distribution factors, and live load ratings were calculated from field test data and compared with values obtained from an independent design assessment.;The results indicate that the Culloden Bridge performs with adequate strength and serviceability under the current 4th edition of the American Association of Safety and Highway Transportation Officials (AASHTO) specifications (2007 with 2008 interims). The live load deflections obtained from static load tests were found to be less than L/1000, as well as those determined analytically. Experimental live load deflection distribution factors were found to be larger than AASHTO factors. Conversely, experimental moment distribution factors were found to be less than AASHTO factors. Experimental and design live load ratings were calculated based on the HL-93 design vehicular live load. In all cases, the experimental and design live load rating factors were found to be greater than 1.0; which indicates that the Culloden Bridge has sufficient capacity
Thermodynamics of black branes in asymptotically Lifshitz spacetimes
Recently, a class of gravitational backgrounds in 3+1 dimensions have been
proposed as holographic duals to a Lifshitz theory describing critical
phenomena in 2+1 dimensions with critical exponent . We continue our
earlier work \cite{Bertoldi:2009vn}, exploring the thermodynamic properties of
the "black brane" solutions with horizon topology . We find that
the black branes satisfy the relation where
is the energy density, is the temperature, and is the
entropy density. This matches the expected behavior for a 2+1 dimensional
theory with a scaling symmetry , .Comment: 8 pages, references added and regroupe
Determination of the Newtonian Gravitational Constant Using Atom Interferometry
We present a new measurement of the Newtonian gravitational constant G based
on cold atom interferometry. Freely falling samples of laser-cooled rubidium
atoms are used in a gravity gradiometer to probe the field generated by nearby
source masses. In addition to its potential sensitivity, this method is
intriguing as gravity is explored by a quantum system. We report a value of
G=6.667 10^{-11} m^{3} kg^{-1} s^{-2}, estimating a statistical uncertainty of
0.011 10^{-11} m^{3} kg^{-1} s^{-2} and a systematic uncertainty of
0.003 10^{-11} m^{3} kg^{-1} s^{-2}. The long-term stability of the instrument
and the signal-to-noise ratio demonstrated here open interesting perspectives
for pushing the measurement accuracy below the 100 ppm level.Comment: 4 figure
Large N gauge theories and topological cigars
We analyze the conjectured duality between a class of double-scaling limits
of a one-matrix model and the topological twist of non-critical superstring
backgrounds that contain the N=2 Kazama-Suzuki SL(2)/U(1) supercoset model. The
untwisted backgrounds are holographically dual to double-scaled Little String
Theories in four dimensions and to the large N double-scaling limit of certain
supersymmetric gauge theories. The matrix model in question is the auxiliary
Dijkgraaf-Vafa matrix model that encodes the F-terms of the above
supersymmetric gauge theories. We evaluate matrix model loop correlators with
the goal of extracting information on the spectrum of operators in the dual
non-critical bosonic string. The twisted coset at level one, the topological
cigar, is known to be equivalent to the c=1 non-critical string at self-dual
radius and to the topological theory on a deformed conifold. The spectrum and
wavefunctions of the operators that can be deduced from the matrix model
double-scaling limit are consistent with these expectations.Comment: 34 page
Near-Infrared Photometry of the High-Redshift Quasar RDJ030117+002025: Evidence for a Massive Starburst at z=5.5
With a redshift of z=5.5 and an optical blue magnitude M_B ~ -24.2 mag (~4.5
10^12 L_sun), RDJ030117+002025 is the most distant optically faint (M_B > -26
mag) quasar known. MAMBO continuum observations at lambda=1.2 mm (185
micrometer rest-frame) showed that this quasar has a far-IR luminosity
comparable to its optical luminosity. We present near-infrared J- and K-band
photometry obtained with NIRC on the Keck I telescope, tracing the slope of the
rest frame UV spectrum of this quasar. The observed spectral index is close to
the value of alpha_nu ~ -0.44 measured in composite spectra of optically-bright
SDSS quasars. It thus appears that the quasar does not suffer from strong dust
extinction, which further implies that its low rest-frame UV luminosity is due
to an intrinsically-faint AGN. The FIR to optical luminosity ratio is then much
larger than that observed for the more luminous quasars, supporting the
suggestion that the FIR emission is not powered by the AGN but by a massive
starburst.Comment: 6 pages, APJ in pres
Thermodynamics of Dyonic Lifshitz Black Holes
Black holes with asymptotic anisotropic scaling are conjectured to be gravity
duals of condensed matter system close to quantum critical points with
non-trivial dynamical exponent z at finite temperature. A holographic
renormalization procedure is presented that allows thermodynamic potentials to
be defined for objects with both electric and magnetic charge in such a way
that standard thermodynamic relations hold. Black holes in asymptotic Lifshitz
spacetimes can exhibit paramagnetic behavior at low temperature limit for
certain values of the critical exponent z, whereas the behavior of AdS black
holes is always diamagnetic.Comment: 26 pages, 4 figure
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