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Full-Text Articles in Physics

Holography, A Covariant C Function, And The Geometry Of The Renormalization Group, Vatche Sahakian Nov 2000

Holography, A Covariant C Function, And The Geometry Of The Renormalization Group, Vatche Sahakian

All HMC Faculty Publications and Research

We propose a covariant geometrical expression for the c function for theories which admit dual gravitational descriptions. We state a c theorem with respect to this quantity and prove it. We apply the expression to a class of geometries, from domain walls in gauged supergravities, to extremal and near extremal Dp-branes, and the AdS Schwarzschild black hole. In all cases, we find agreement with expectations.


The Phases Of 2d Ncos, Vatche Sahakian Oct 2000

The Phases Of 2d Ncos, Vatche Sahakian

All HMC Faculty Publications and Research

We study the phases of the (1+1)-dimensional Non-Commutative Open String theory on a circle. We find that the length scale of non-commutativity increases at strong coupling, the coupling in turn being dressed by a power of D-string charge. The system is stringy at around this length scale, with dynamics involving an interplay between the open and wrapped closed strings sectors. Above this energy scale and at strong coupling, and below it at weak coupling, the system acquires a less stringy character. The near horizon geometry of the configuration exhibits several intriguing features, such as a flip in the dilaton field …


Comments On D Branes And The Renormalization Group, Vatche Sahakian Jun 2000

Comments On D Branes And The Renormalization Group, Vatche Sahakian

All HMC Faculty Publications and Research

We review the de Boer-Verlinde-Verlinde formalism for the renormalization group in the context of Dp-brane vacua for p < 5. We comment on various aspects of the dictionary between bulk and boundary and relate the discussion to the Randall-Sundrum scenario. We find that the gravitational coupling for the Randall-Sundrum gravity on the Dp-brane worldvolume is dressed by the c-function of the Yang-Mills theory. We compute the beta function and find the expected uneventful flow prescribed by the classical dimension of the Yang-Mills operator.


An Optical Coherence Microscope For 3-Dimensional Imaging In Developmental Biology, Barbara M. Hoeling, Andrew D. Fernandez, Richard C. Haskell, Eric Huang, Whittier R. Myers, Daniel C. Petersen, Sharon E. Ungersma, Ruye Wang, Mary E. Williams, Scott E. Fraser Mar 2000

An Optical Coherence Microscope For 3-Dimensional Imaging In Developmental Biology, Barbara M. Hoeling, Andrew D. Fernandez, Richard C. Haskell, Eric Huang, Whittier R. Myers, Daniel C. Petersen, Sharon E. Ungersma, Ruye Wang, Mary E. Williams, Scott E. Fraser

All HMC Faculty Publications and Research

An optical coherence microscope (OCM) has been designed and constructed to acquire 3-dimensional images of highly scattering biological tissue. Volume-rendering software is used to enhance 3-D visualization of the data sets. Lateral resolution of the OCM is 5 mm (FWHM), and the depth resolution is 10 mm (FWHM) in tissue. The design trade-offs for a 3-D OCM are discussed, and the fundamental photon noise limitation is measured and compared with theory. A rotating 3-D image of a frog embryo is presented to illustrate the capabilities of the instrument.


Disorder-Induced Desynchronization In A 2x2 Circular Josephson Junction Array, Adam S. Landsberg Feb 2000

Disorder-Induced Desynchronization In A 2x2 Circular Josephson Junction Array, Adam S. Landsberg

WM Keck Science Faculty Papers

Analytical results are presented which characterize the behavior of a dc-biased, two-dimensional circular array of overdamped Josephson junctions subject to increasing levels of disorder. It is shown that high levels of disorder can abruptly destroy the synchronous functioning of the array. We identify the transition boundary between synchronized and desynchronized behavior, along with the mechanism responsible for the loss of frequency locking. Comparisons with recent results for arrays with rectangular lattice geometries are described.