Minimal area submanifolds in AdS x compact

We describe the asymptotic behavior of minimal area submanifolds in product spacetimes of an asymptotically hyperbolic space times a compact internal manifold. In particular, we find that unlike the case of a minimal area submanifold just in an asymptotically hyperbolic space, the internal part of the boundary submanifold is constrained to be itself a minimal area submanifold. For applications to holography, this tells us what are the allowed "flavor branes" that can be added to a holographic field theory. We also give a compact geometric expression for the spectrum of operator dimensions associated with the slipping modes of the submanifold in the internal space. We illustrate our results with several examples, including some that haven't appeared in the literature before.Comment: 24 pages, no figure

The Stress-Energy Tensor of Flavor Fields from AdS/CFT

We use the AdS/CFT correspondence to study the transport properties of massive N=2 hypermultiplet fields in an N=4 SU(Nc) super-Yang-Mills theory plasma in the large Nc, large 't Hooft coupling limit, and in the presence of a baryon number chemical potential and external electric and magnetic fields. In particular, we compute the flavor fields' contribution to the stress-energy tensor. We find infrared divergences in the stress-energy tensor, arising from the flavor fields' constant rate of energy and momentum loss. We regulate these divergences and extract the energy and momentum loss rates from the divergent terms. We also check our result in various limits in which the divergences are absent. The supergravity dual is a system of D7-branes, with a particular configuration of worldvolume fields, probing an AdS-Schwarzschild background. The supergravity calculation amounts to computing the stress-energy tensor of the D7-branes.Comment: 32 pages; v2, added one footnote in section 2.2, added one reference, version published in JHE

Critical Exponents from AdS/CFT with Flavor

We use the AdS/CFT correspondence to study the thermodynamics of massive N=2 supersymmetric hypermultiplet flavor fields coupled to N=4 supersymmetric SU(Nc) Yang-Mills theory, formulated on curved four-manifolds, in the limits of large Nc and large 't Hooft coupling. The gravitational duals are probe D-branes in global thermal AdS. These D-branes may undergo a topology-changing transition in the bulk. The D-brane embeddings near the point of the topology change exhibit a scaling symmetry. The associated scaling exponents can be either real- or complex-valued. Which regime applies depends on the dimensionality of a collapsing submanifold in the critical embedding. When the scaling exponents are complex-valued, a first-order transition associated with the flavor fields appears in the dual field theory. Real scaling exponents are expected to be associated with a continuous transition in the dual field theory. For one example with real exponents, the D7-brane, we study the transition in detail. We find two field theory observables that diverge at the critical point, and we compute the associated critical exponents. We also present analytic and numerical evidence that the transition expresses itself in the meson spectrum as a non-analyticity at the critical point. We argue that the transition we study is a true phase transition only when the 't Hooft coupling is strictly infinite.Comment: 31 pages, 21 eps files in 12 figures; v2 added one reference and one footnote, version published in JHE

Bedside differentiation of vestibular neuritis from central "vestibular pseudoneuritis".

Acute unilateral peripheral and central vestibular lesions can cause similar signs and symptoms, but they require different diagnostics and management. We therefore correlated clinical signs to differentiate vestibular neuritis (40 patients) from central ‘‘vestibular pseudoneuritis’’ (43 patients) in the acute situation with the final diagnosis assessed by neuroimaging. Skew deviation was the only specific but non-sensitive (40%) sign for pseudoneuritis. None of the other isolated signs (head thrust test, saccadic pursuit, gaze evoked nystagmus, subjective visual vertical) were reliable; however, multivariate logistic regression increased their sensitivity and specificity to 92%

Mesons from global Anti-de Sitter space

In the context of gauge/gravity duality, we study both probe D7-- and probe D5--branes in global Anti-de Sitter space. The dual field theory is N=4 theory on R x S^3 with added flavour. The branes undergo a geometrical phase transition in this geometry as function of the bare quark mass m_q in units of 1/R with R the S^3 radius. The meson spectra are obtained from fluctuations of the brane probes. First, we study them numerically for finite quark mass through the phase transition. Moreover, at zero quark mass we calculate the meson spectra analytically both in supergravity and in free field theory on R x S^3 and find that the results match: For the chiral primaries, the lowest level is given by the zero point energy or by the scaling dimension of the operator corresponding to the fluctuations, respectively. The higher levels are equidistant. Similar results apply to the descendents. Our results confirm the physical interpretation that the mesons cannot pair-produce any further when their zero-point energy exceeds their binding energy.Comment: 43 pages, 8 figures, references edited, few typos corrected, updated to match the published versio

Robust Super-resolution by Fusion of Interpolated Frames for Color and Grayscale Images

Multi-frame super-resolution (SR) processing seeks to overcome undersampling issues that can lead to undesirable aliasing artifacts in imaging systems. A key factor in effective multi-frame SR is accurate subpixel inter-frame registration. Accurate registration is more difficult when frame-to-frame motion does not contain simple global translation and includes locally moving scene objects. SR processing is further complicated when the camera captures full color by using a Bayer color filter array (CFA). Various aspects of these SR challenges have been previously investigated. Fast SR algorithms tend to have difficulty accommodating complex motion and CFA sensors. Furthermore, methods that can tolerate these complexities tend to be iterative in nature and may not be amenable to real-time processing. In this paper, we present a new fast approach for performing SR in the presence of these challenging imaging conditions. We refer to the new approach as Fusion of Interpolated Frames (FIF) SR. The FIF SR method decouples the demosaicing, interpolation, and restoration steps to simplify the algorithm. Frames are first individually demosaiced and interpolated to the desired resolution. Next, FIF uses a novel weighted sum of the interpolated frames to fuse them into an improved resolution estimate. Finally, restoration is applied to improve any degrading camera effects. The proposed FIF approach has a lower computational complexity than many iterative methods, making it a candidate for real-time implementation. We provide a detailed description of the FIF SR method and show experimental results using synthetic and real datasets in both constrained and complex imaging scenarios. Experiments include airborne grayscale imagery and Bayer CFA image sets with affine background motion plus local motion

Spikes and diffusion waves in one-dimensional model of chemotaxis

We consider the one-dimensional initial value problem for the viscous transport equation with nonlocal velocity $u_t = u_{xx} - \left(u (K^\prime \ast u)\right)_{x}$ with a given kernel $K'\in L^1(\R)$. We show the existence of global-in-time nonnegative solutions and we study their large time asymptotics. Depending on $K'$, we obtain either linear diffusion waves ({\it i.e.}~the fundamental solution of the heat equation) or nonlinear diffusion waves (the fundamental solution of the viscous Burgers equation) in asymptotic expansions of solutions as $t\to\infty$. Moreover, for certain aggregation kernels, we show a concentration of solution on an initial time interval, which resemble a phenomenon of the spike creation, typical in chemotaxis models

Hot Defect Superconformal Field Theory in an External Magnetic Field

In this paper we investigate the influence of an external magnetic field on a flavoured holographic gauge theory dual to the D3/D5 intersection at finite temperature. Our study shows that the external magnetic field has a freezing effect on the confinement/ deconfinement phase transition. We construct the corresponding phase diagram. We investigate some thermodynamic quantities of the theory. A study of the entropy reveals enhanced relative jump of the entropy at the "chiral" phase transition. A study of the magnetization shows that both the confined and deconfined phases exhibit diamagnetic response. The diamagnetic response in the deconfined phase has a stronger temperature dependence reflecting the temperature dependence of the conductivity. We study the meson spectrum of the theory and analyze the stability of the different phases looking at both normal and quasi-normal semi-classical excitations. For the symmetry breaking phase we analyze the corresponding pseudo-Goldstone modes and prove that they satisfy non-relativistic dispersion relation.Comment: 42 pages, 14 figure

Robust Super-resolution by Fusion of Interpolated Frames for Color and Grayscale Images

Multi-frame super-resolution (SR) processing seeks to overcome undersampling issues that can lead to undesirable aliasing artifacts in imaging systems. A key factor in effective multi-frame SR is accurate subpixel inter-frame registration. Accurate registration is more difficult when frame-to-frame motion does not contain simple global translation and includes locally moving scene objects. SR processing is further complicated when the camera captures full color by using a Bayer color filter array (CFA). Various aspects of these SR challenges have been previously investigated. Fast SR algorithms tend to have difficulty accommodating complex motion and CFA sensors. Furthermore, methods that can tolerate these complexities tend to be iterative in nature and may not be amenable to real-time processing. In this paper, we present a new fast approach for performing SR in the presence of these challenging imaging conditions. We refer to the new approach as Fusion of Interpolated Frames (FIF) SR. The FIF SR method decouples the demosaicing, interpolation, and restoration steps to simplify the algorithm. Frames are first individually demosaiced and interpolated to the desired resolution. Next, FIF uses a novel weighted sum of the interpolated frames to fuse them into an improved resolution estimate. Finally, restoration is applied to improve any degrading camera effects. The proposed FIF approach has a lower computational complexity than many iterative methods, making it a candidate for real-time implementation. We provide a detailed description of the FIF SR method and show experimental results using synthetic and real datasets in both constrained and complex imaging scenarios. Experiments include airborne grayscale imagery and Bayer CFA image sets with affine background motion plus local motion

Adaptive Wiener Filter Super-Resolution of Color Filter Array Images

Digital color cameras using a single detector array with a Bayer color filter array (CFA) require interpolation or demosaicing to estimate missing color information and provide full-color images. However, demosaicing does not specifically address fundamental undersampling and aliasing inherent in typical camera designs. Fast non-uniform interpolation based super-resolution (SR) is an attractive approach to reduce or eliminate aliasing and its relatively low computational load is amenable to real-time applications. The adaptive Wiener filter (AWF) SR algorithm was initially developed for grayscale imaging and has not previously been applied to color SR demosaicing. Here, we develop a novel fast SR method for CFA cameras that is based on the AWF SR algorithm and uses global channel-to-channel statistical models. We apply this new method as a stand-alone algorithm and also as an initialization image for a variational SR algorithm. This paper presents the theoretical development of the color AWF SR approach and applies it in performance comparisons to other SR techniques for both simulated and real data