Towards a holographic realization of the quarkyonic phase

Large-N_c QCD matter at intermediate baryon density and low temperatures has been conjectured to be in the so-called quarkyonic phase, i.e., to have a quark Fermi surface and on top of it a confined spectrum of excitations. It has been suggested that the presence of the quark Fermi surface leads to a homogeneous phase with restored chiral symmetry, which is unstable towards creating condensates breaking both the chiral and translational symmetry. Motivated by these exotic features, we investigate properties of cold baryonic matter in the single flavor Sakai-Sugimoto model searching for a holographic realization of the quarkyonic phase. We use a simplified mean-field description and focus on the regime of parametrically large baryon densities, of the order of the square of the 't Hooft coupling, as they turn out to lead to new physical effects similar to the ones occurring in the quarkyonic phase. One effect, the appearance of a particular marginally stable mode breaking translational invariance and linked with the presence of the Chern-Simons term in the flavor brane Lagrangian, is known to occur in the deconfined phase of the Sakai-Sugimoto model, but turns out to be absent here. The other, completely new phenomenon that we, preliminarily, study using strong simplifying assumptions are density-enhanced interactions of the flavor brane gauge field with holographically represented baryons. These seem to significantly affect the spectrum of vector and axial mesons and might lead to approximate chiral symmetry restoration in the lowest part of the spectrum, where the mesons start to qualitatively behave like collective excitations of the dense baryonic medium. We discuss the relevance of these effects for holographic searches of the quarkyonic phase and conclude with a discussion of various subtleties involved in constructing a mean-field holographic description of a dense baryonic medium.Comment: 31 pages, 16 figures; v2: inset plot in Fig. 10 removed, coloring in Fig. 13 fixed, typos fixed, matches published versio

Entanglement, Holography and Causal Diamonds

We argue that the degrees of freedom in a d-dimensional CFT can be re-organized in an insightful way by studying observables on the moduli space of causal diamonds (or equivalently, the space of pairs of timelike separated points). This 2d-dimensional space naturally captures some of the fundamental nonlocality and causal structure inherent in the entanglement of CFT states. For any primary CFT operator, we construct an observable on this space, which is defined by smearing the associated one-point function over causal diamonds. Known examples of such quantities are the entanglement entropy of vacuum excitations and its higher spin generalizations. We show that in holographic CFTs, these observables are given by suitably defined integrals of dual bulk fields over the corresponding Ryu-Takayanagi minimal surfaces. Furthermore, we explain connections to the operator product expansion and the first law of entanglement entropy from this unifying point of view. We demonstrate that for small perturbations of the vacuum, our observables obey linear two-derivative equations of motion on the space of causal diamonds. In two dimensions, the latter is given by a product of two copies of a two-dimensional de Sitter space. For a class of universal states, we show that the entanglement entropy and its spin-three generalization obey nonlinear equations of motion with local interactions on this moduli space, which can be identified with Liouville and Toda equations, respectively. This suggests the possibility of extending the definition of our new observables beyond the linear level more generally and in such a way that they give rise to new dynamically interacting theories on the moduli space of causal diamonds. Various challenges one has to face in order to implement this idea are discussed.Comment: 84 pages, 12 figures; v2: expanded discussion on constraints in section 7, matches published versio

К расчету токопрохождения через инфлектор бетатрона

Рассмотрено движение цилиндрического релятивистского электронного пучка в плоском инфлекторе. Получена зависимость коэффициента токопрохождения инфлектора от параметров инфлектора и электронного пучка. Утверждается, что полученной зависимостью можно пользоваться для оценок величины коэффициента токопрохождения в цилиндрическом инфлекторе и в цилиндрическом инфлекторе обратной кривизны, если средний радиус кривизны указанных инфлекторов достаточно большой

On the Two-View Geometry of Unsynchronized Cameras

We present new methods for simultaneously estimating camera geometry and time shift from video sequences from multiple unsynchronized cameras. Algorithms for simultaneous computation of a fundamental matrix or a homography with unknown time shift between images are developed. Our methods use minimal correspondence sets (eight for fundamental matrix and four and a half for homography) and therefore are suitable for robust estimation using RANSAC. Furthermore, we present an iterative algorithm that extends the applicability on sequences which are significantly unsynchronized, finding the correct time shift up to several seconds. We evaluated the methods on synthetic and wide range of real world datasets and the results show a broad applicability to the problem of camera synchronization.Comment: 12 pages, 9 figures, Computer Vision and Pattern Recognition (CVPR) 201

A hole-ographic spacetime

We embed spherical Rindler space -- a geometry with a spherical hole in its center -- in asymptotically AdS spacetime and show that it carries a gravitational entropy proportional to the area of the hole. Spherical AdS-Rindler space is holographically dual to an ultraviolet sector of the boundary field theory given by restriction to a strip of finite duration in time. Because measurements have finite durations, local observers in the field theory can only access information about bounded spatial regions. We propose a notion of Residual Entropy that captures uncertainty about the state of a system left by the collection of local, finite-time observables. For two-dimensional conformal field theories we use holography and the strong subadditivity of entanglement to propose a formula for Residual Entropy and show that it precisely reproduces the areas of circular holes in AdS3. Extending the notion to field theories on strips with variable durations in time, we show more generally that Residual Entropy computes the areas of all closed, inhomogenous curves on a spatial slice of AdS3. We discuss the extension to higher dimensional field theories, the relation of Residual Entropy to entanglement between scales, and some implications for the emergence of space from the RG flow of entangled field theories.Comment: v3: minor typos correcte

Environmentally assisted fatigue of superelastic NiTi

Superelastic NiTi implants transforming cyclically in body fluids suffer from fatigue failures which are extremely difficult to predict. This clearly points out towards environmental effects promoting surface dominated fatigue degradation. The specialty of phase transforming NiTi shape memory alloy is that either the parent austenite or the product martensite phase exist at the excessively deforming metal/liquid interface covered by the thin TiO2 surface. In order to explore the environmental effects at such mechanically active metal/liquid interface, we have developed dedicated electrochemical apparatus and methods combining electrochemical cell, mechanical tester and thermal chamber. We are able to follow and/or control the mechanically triggered periodical breakdown/passivation process on the metal/liquid interface occurring during cyclic tensile tests on NiTi wires and springs in fluids. In this way we are able to analyze the effect of surface finishing treatments on fatigue performance and/or control it electrochemically. In this talk, we will introduce two in-situ electrochemical methods especially open circuit potential and potentiostatic polarization applied during fatigue testing. We will focus on the problem of non-stationary thermodynamic equilibrium established at the mechanochemically loaded wire surface. Kinetics of the surface reactions encountered during this type of environmental fatigue testing will be revealed. SIMS depth profile analysis and chemical imaging of the surfaces of fatigued wires was employed to prove the assumed electrochemical activity upon cycling, particularly to the hydrogen absorption and growth of passive oxide layer within cracks. Microcracks forming on the surface of fatigued wires were observed by 3D SEM/FIB sectioning method. Based on the results, mechanisms of environmental fatigue degradation of NiTi implants deforming cyclically in body fluids will be proposed