Showing papers in "Lecture Notes in Physics in 2013"
TL;DR: In this paper, the effect of a magnetic field in the linear sigma model has been studied in the context of holographic metamagnetworks. But it is not shown that the effect can be applied to magnetized condensed matter systems.
Abstract: From the Contents: Chiral magnetic spirals.- Magnetized matter in the Sakai-Sugimoto model.- Charge-dependent correlations in heavy ion collisions.- Superconductivity from rho meson condensation in QCD.- Lattice studies of QCD phase transitions in a magnetic field.- Holographic Metamagnetism.- Dense quark matter in a magnetic field.- Effects of a magnetic field in the linear sigma model.- Chiral Magnetic effect II.- Debye screening in magnetic field through holography.- Holographic magnetized fermions.- Chiral magnetic effect in holographic models.- Applications of the AdS/CFT correspondence to magnetized condensed matter systems.
241 citations
TL;DR: In this article, a volume of Lecture Notes in Physics on strongly interacting matter in magnetic fields is presented, which combines contributions written by a number of experts on different aspects of the problem.
Abstract: This is an introduction to the volume of Lecture Notes in Physics on “Strongly interacting matter in magnetic fields”. The volume combines contributions written by a number of experts on different aspects of the problem. The response of QCD matter to intense magnetic fields has attracted a lot of interest recently. On the theoretical side, this interest stems from the possibility to explore the plethora of novel phenomena arising from the interplay of magnetic field with QCD dynamics. On the experimental side, the interest is motivated by the recent results on the behavior of quark-gluon plasma in a strong magnetic field created in relativistic heavy ion collisions at RHIC and LHC. The purpose of this introduction is to provide a brief overview and a guide to the individual contributions where these topics are covered in detail.
173 citations
TL;DR: In this paper, the authors review the calculation of the anomalous transport coefficients via Kubo formulae with a particular emphasis on the contribution of the mixed gauge-gravitational anomaly.
Abstract: Chiral anomalies have profound impact on the transport properties of relativistic fluids. In four dimensions there are different types of anomalies, pure gauge and mixed gauge-gravitational anomalies. They give rise to two new non-dissipative transport coefficients, the chiral magnetic conductivity and the chiral vortical conductivity. They can be calculated from the microscopic degrees of freedom with the help of Kubo formulae. We review the calculation of the anomalous transport coefficients via Kubo formulae with a particular emphasis on the contribution of the mixed gauge-gravitational anomaly.
144 citations
TL;DR: The magnetic catalysis phenomenon is defined as an enhancement of dynamical symmetry breaking by an external magnetic field as discussed by the authors, and it is a universal and model-independent phenomenon, which implies a wide range of potential applications: from certain types of solid state systems to models in cosmology, particle and nuclear physics.
Abstract: We give an overview of the magnetic catalysis phenomenon. In the framework of quantum field theory, magnetic catalysis is broadly defined as an enhancement of dynamical symmetry breaking by an external magnetic field. We start from a brief discussion of spontaneous symmetry breaking and the role of a magnetic field in its a dynamics. This is followed by a detailed presentation of the essential features of the phenomenon. In particular, we emphasize that the dimensional reduction plays a profound role in the pairing dynamics in a magnetic field. Using the general nature of underlying physics and its robustness with respect to interaction types and model content, we argue that magnetic catalysis is a universal and model-independent phenomenon. In support of this claim, we show how magnetic catalysis is realized in various models with short-range and long-range interactions. We argue that the general nature of the phenomenon implies a wide range of potential applications: from certain types of solid state systems to models in cosmology, particle and nuclear physics. We finish the review with general remarks about magnetic catalysis and an outlook for future research.
131 citations
TL;DR: In this paper, the Cerenkov Effect Revisited: From swimming Ducks to zero modes in Gravitational Analogues, some Aspects of Dispersive Horizons: Lessons from Surface Waves.
Abstract: Black Holes and Hawking Radiation in Spacetime and its Analogues.- Survey of Analogue Spacetimes.- Cosmological Particle Creation in the Lab.- Irrotational, Two-Dimensional Surface Waves in Fluids.- The Basics of Water Waves Theory for Analogue Gravity.- The Cerenkov Effect Revisited: From Swimming Ducks to Zero Modes in Gravitational Analogues.- Some Aspects of Dispersive Horizons: Lessons from Surface Waves.- Classical Aspects of Hawking Radiation Verified in Analogue Gravity Experiment.- Understanding Hawking Radiation from Models of Atomic Bose-Einstein Condensates.- Transformation Optics.- Laser Pulse Analogues for Gravity.- An All-Optical Event Horizon in an Optical Analogue of a Laval Nozzle.- Lorentz Breaking Effective Field Theory and Observational Tests.- The Topology of Quantum Vacuum.- Einstein^2 :Brownian Motion Meets General Relativity.- Astrophysical Black Holes: Evidence of a Horizon?.
127 citations
TL;DR: In this article, a particle approach is proposed to describe the formation of spatially extended patterns in all kinds of physical, chemical, biological and other systems, where the underlying field equations are reduced to order-parameter equations with a finite and possibly small number of degrees of freedom, without losing the important information.
Abstract: A major goal of natural science is to understand the formation of spatiallyextended patterns in all kinds of physical, chemical, biological and other systems. In many cases, it is advantageous to interpret the overall pattern under consideration in terms of a superposition of certain spatially well-localized elementary patterns that we may refer to as “particles”. In the simplest case, all these particles are of the same kind and the complex behavior of the extended pattern can be described in terms of simple individual properties of the particles and their interaction. A clear illustrative example for this approach is the concept of atoms. In this case, the elementary pattern or particle is the atom and the complex spatially-extended pattern is, e.g., the crystal. From a theoretical point of view, pattern forming systems are described by field equations with infinitely many degrees of freedom. However, a powerful technique for describing their temporal evolution is to use a “particle approach”. In this approach, well-localized solutions of the field equation are viewed as particles. The dynamic behavior and the interaction of these particles are described by ordinary differential equations, using center-of-mass co-ordinates and possibly some other variables. The decisive advantage of such an approach is that the underlying field equations, with infinitely many degrees of freedom, can be reduced to order-parameter equations with a finite and possibly small number of degrees of freedom, without losing the important information. An extremely powerful and far-reaching application is the notion of atoms. We recall that macroscopic physical systems can be separated into two classes, according to their long-time behavior. One class approaches thermodynamic equilibrium, resulting in a vanishing exchange of energy with the surroundings. The second class is characterized by external driving “forces” which lead to a finite energy transfer to the system, and, correspondingly, to a finite dissipation in the long run. For the first class of systems, general techniques to find physical solutions have been developed. Systems in thermodynamic equilibrium can be described by a thermodynamic potential, of which one has to find the absolute
112 citations
TL;DR: In this article, a phenomenological analysis of present experimental searches for local parity violation manifested through the Chiral Magnetic Effect is provided, and the relevant correlation functions used for the measurements are discussed.
Abstract: We provide a phenomenological analysis of present experimental searches for local parity violation manifested through the Chiral Magnetic Effect. We introduce and discuss the relevant correlation functions used for the measurements. Our analysis of the available data from both RHIC and LHC shows that the present experimental evidence for the Chiral Magnetic Effect is rather ambiguous. We further discuss in some detail various background contributions due to conventional physics, which need to be understood quantitatively in order to draw a definitive conclusion about the existence of local parity violation in heavy ion collisions.
108 citations
TL;DR: In this article, the basic ideas of the asymptotic safety approach to quantum Einstein gravity (QEG) were introduced, and the background for recent work on the possibly multi-fractal structure of the QEG space-times.
Abstract: These lecture notes introduce the basic ideas of the asymptotic safety approach to quantum Einstein gravity (QEG). In particular they provide the background for recent work on the possibly multi-fractal structure of the QEG space-times. Implications of asymptotic safety for the cosmology of the early Universe are also discussed.
82 citations
TL;DR: In this paper, the authors review derivations of the chiral magnetic effect (ChME) in hydrodynamic approximation and show that the ChME is not renormalized: in the hydrodynamics approximation it remains the same as for non-interacting chiral fermions moving in an external magnetic field.
Abstract: We review derivations of the chiral magnetic effect (ChME) in hydrodynamic approximation. The reader is assumed to be familiar with the basics of the effect. The main challenge now is to account for the strong interactions between the constituents of the fluid. The main result is that the ChME is not renormalized: in the hydrodynamic approximation it remains the same as for non-interacting chiral fermions moving in an external magnetic field. The key ingredients in the proof are general laws of thermodynamics and the Adler-Bardeen theorem for the chiral anomaly in external electromagnetic fields. The chiral magnetic effect in hydrodynamics represents a macroscopic manifestation of a quantum phenomenon (chiral anomaly). Moreover, one can argue that the current induced by the magnetic field is dissipation free and talk about a kind of “chiral superconductivity”. More precise description is a quantum ballistic transport along magnetic field taking place in equilibrium and in absence of a driving force. The basic limitation is the exact chiral limit while temperature—excitingly enough—does not seemingly matter. What is still lacking, is a detailed quantum microscopic picture for the ChME in hydrodynamics. Probably, the chiral currents propagate through lower-dimensional defects, like vortices in superfluid. In case of superfluid, the prediction for the chiral magnetic effect remains unmodified although the emerging dynamical picture differs from the standard one.
79 citations
TL;DR: In this article, the authors discuss recent results and future prospects regarding the investigation, by lattice simulations, of the nonperturbative properties of QCD and of its phase diagram in presence of magnetic or chromomagnetic background fields.
Abstract: We discuss recent results and future prospects regarding the investigation, by lattice simulations, of the non-perturbative properties of QCD and of its phase diagram in presence of magnetic or chromomagnetic background fields. After a brief introduction to the formulation of lattice QCD in presence of external fields, we focus on studies regarding the effects of external fields on chiral symmetry breaking, on its restoration at finite temperature and on deconfinement. We conclude with a few comments regarding the effects of electromagnetic background fields on gluodynamics.
75 citations
TL;DR: The interpretation of the produced current is indeed very non-trivial and it involves a lot of confusions that have not been resolved as mentioned in this paper, and some considerations would lead us to even more questions than elucidations.
Abstract: My personal views of the Chiral Magnetic Effect are presented, which starts with a story about how we came up with the electric-current formula and continues to unsettled subtleties in the formula. There are desirable features in the formula of the Chiral Magnetic Effect but some considerations would lead us to even more questions than elucidations. The interpretation of the produced current is indeed very non-trivial and it involves a lot of confusions that have not been resolved.
TL;DR: In this paper, the surface of the chiral phase transition in the three-dimensional parameter space of temperature, baryon chemical potential and magnetic field was investigated in two different approaches, the field-theoretical Nambu-Jona-Lasinio (NJL) model and the holographic Sakai-Sugimoto model.
Abstract: We investigate the surface of the chiral phase transition in the three-dimensional parameter space of temperature, baryon chemical potential and magnetic field in two different approaches, the field-theoretical Nambu–Jona-Lasinio (NJL) model and the holographic Sakai–Sugimoto model. The latter is a top–down approach to a gravity dual of QCD with an asymptotically large number of colors and becomes, in a certain limit, dual to an NJL-like model. Our main observation is that, at nonzero chemical potential, a magnetic field can restore chiral symmetry, in apparent contrast to the phenomenon of magnetic catalysis. This “inverse magnetic catalysis” occurs in the Sakai–Sugimoto model and, for sufficiently large coupling, in the NJL model and is related to the physics of the lowest Landau level. While in most parts our discussion is a pedagogical review of previously published results, we include new analytical results for the NJL approach and a thorough comparison of inverse magnetic catalysis in the two approaches.
TL;DR: In this paper, the authors review the latest results on both components for planets in circular orbits, with special emphasis on the various processes that give rise to a large corotation torque and those contributing to its saturation.
Abstract: Planetary migration is the process by which a forming planet undergoes a drift of its semi-major axis caused by the tidal interaction with its parent protoplanetary disc. One of the key quantities to assess the migration of embedded planets is the tidal torque between the disc and the planet, which has two components: the Lindblad torque and the corotation torque. We review the latest results on both components for planets in circular orbits, with special emphasis on the various processes that give rise to a large corotation torque and those contributing to its saturation. The additional corotation torque could help address the shortcomings that have recently been exposed in models of planet population synthesis. We also review recent results concerning the migration of giant planets that carve gaps in the disc (type II migration) and the migration of sub-giant planets that open partial gaps in massive discs (type III migration).
TL;DR: In this article, a review describes how the idea of galactic tides has emerged thanks to advances in numerical simulations, from the first simulations that included tens of particles to the most sophisticated ones with tens of millions of them and state-of-the-art hydrodynamical prescriptions.
Abstract: Long tails and streams of stars are the most noticeable traces of galaxy collisions. However, their tidal origin was recognized only less than 50 years ago and more than 10 years after their first observations. This review describes how the idea of galactic tides has emerged thanks to advances in numerical simulations, from the first simulations that included tens of particles to the most sophisticated ones with tens of millions of them and state-of-the-art hydrodynamical prescriptions. Theoretical aspects pertaining to the formation of tidal tails are then presented. The third part turns to observations and underlines the need for collecting deep multi-wavelength data to tackle the variety of physical processes exhibited by collisional debris. Tidal tails are not just stellar structures, but turn out to contain all the components usually found in galactic disks, in particular atomic/molecular gas and dust. They host star-forming complexes and are able to form star-clusters or even second-generation dwarf galaxies. The final part of the review discusses what tidal tails can tell us (or not) about the structure and the content of present-day galaxies, including their dark components, and explains how they may be used to probe the past evolution of galaxies and the history of their mass assembly. On-going deep wide-field surveys disclose many new low-surface brightness structures in the nearby Universe, offering great opportunities for attempting galactic archeology with tidal tails.
TL;DR: In this paper, an analogy between the propagation of fields on a curved spacetime and shallow water waves in an open channel flow is presented. But the authors do not consider the effects of a streamlined obstacle on the propagation.
Abstract: There is an analogy between the propagation of fields on a curved spacetime and shallow water waves in an open channel flow. By placing a streamlined obstacle into an open channel flow we create a region of high velocity over the obstacle that can include wave horizons. Long (shallow water) waves propagating upstream towards this region are blocked and converted into short (deep water) waves. This is the analogue of the stimulated Hawking emission by a white hole (the time inverse of a black hole). The measurements of amplitudes of the converted waves demonstrate that they appear in pairs and are classically correlated; the spectra of the conversion process is described by a Boltzmann-distribution; and the Boltzmann-distribution is determined by the change in flow across the white hole horizon.
TL;DR: In this article, the effect of the magnetic background on chiral symmetry restoration and deconfinement at finite temperature was discussed. And the magnetic susceptibility of the chiral condensate and the quark polarization at zero temperature.
Abstract: In this chapter, we discuss several aspects of the theory of strong interactions in presence of a strong magnetic background. In particular, we summarize our results on the effect of the magnetic background on chiral symmetry restoration and deconfinement at finite temperature. Moreover, we compute the magnetic susceptibility of the chiral condensate and the quark polarization at zero temperature. Our theoretical framework is given by chiral models: the Nambu-Jona-Lasinio (NJL), the Polyakov improved NJL (or PNJL) and the Quark-Meson (QM) models. We also compare our results with the ones obtained by other groups.
TL;DR: In this paper, the authors present an overview of the relationship between quantum gravity and cosmology and observeational status of quantum cosmology, and propose a method for quantum cosmologies.
Abstract: Part I Quantum Gravity.- Part II Quantum Cosmology.- Part III Observational Status.- Index.
TL;DR: The goal of the lecture is to present a broad perspective on loop quantum gravity and cosmology for young researchers which would serve as an introduction to lectures by Rovelli and Bojowald as mentioned in this paper.
Abstract: The goal of the lecture is to present a broad perspective on loop quantum gravity and cosmology for young researchers which would serve as an introduction to lectures by Rovelli and Bojowald. The first part is addressed to beginning students and the second to young researchers who are already working in quantum gravity.
TL;DR: In this article, the authors investigate how the outputs of models depend on the prescriptions used for the diffusion coefficients included in the shellular rotating models and discuss their impacts on the evolutionary tracks and lifetimes of the Main Sequence (MS) phase, the changes of the surface composition and velocities during the MS phase, and the distribution of the core helium lifetime in the blue and red parts of the HR diagram.
Abstract: The rotation of stars has many interesting and important consequences for the photometric and chemical evolution of galaxies. Many of the predictions of models of stellar rotation are now compared with observations of surface abundances and velocities, with interferometric studies of fast rotating stars, with internal rotation profiles as they can be deduced by asteroseismology, to cite just a few observational constraints. In this paper, we investigate how the outputs of models depend on the prescriptions used for the diffusion coefficients included in the shellular rotating models. After recalling the various prescriptions found in the literature, we discuss their impacts on the evolutionary tracks and lifetimes of the Main-Sequence (MS) phase, the changes of the surface composition and velocities during the MS phase, the distribution of the core helium lifetime in the blue and red parts of the HR diagram, the extensions of the blue loops, the evolution of the angular momentum of the core, and the synthesis of primary nitrogen in fast-rotating metal-poor massive stars. While some of these outputs depend only slightly on the prescriptions used (for instance, the evolution of the surface velocities), most of them show a significant dependence. The models which best fit the changes of the surface abundances are those computed with the vertical shear diffusion coefficient of Maeder (Astron. Astrophys. 321:134–144, 1997) and the horizontal shear diffusion coefficient by Zahn (Astron. Astrophys. 265:115–132, 1992).
TL;DR: In this article, the influence of a magnetic background on the phase diagram of strong interactions and how the chiral and deconfining transitions can be affected is discussed, and results for both transitions obtained in the framework of the linear sigma model coupled to quarks and to the Polyakov loop are presented.
Abstract: We review the influence of a magnetic background on the phase diagram of strong interactions and how the chiral and deconfining transitions can be affected. First we summarize results for both transitions obtained in the framework of the linear sigma model coupled to quarks and to the Polyakov loop, and how they compare to other effective model approaches and to lattice QCD. Then we discuss the outcome of the magnetic MIT bag model that yields a behavior for the critical deconfining temperature which is compatible with recent lattice results and magnetic catalysis. The qualitative success of the magnetic MIT bag model hints to T c being a confinement-driven quantity, and leads us to the discussion of its behavior as predicted within the large-N c limit of QCD, which is also in line with the most recent lattice QCD results provided that quarks behave paramagnetically.
TL;DR: In this article, the authors review the mechanisms via which an external magnetic field can affect the ground state of cold and dense quark matter and discuss the equation of state (EoS) of MCFL matter for a large range of field values.
Abstract: We review the mechanisms via which an external magnetic field can affect the ground state of cold and dense quark matter. In the absence of a magnetic field, at asymptotically high densities, cold quark matter is in the Color-Flavor-Locked (CFL) phase of color superconductivity characterized by three scales: the superconducting gap, the gluon Meissner mass, and the baryonic chemical potential. When an applied magnetic field becomes comparable with each of these scales, new phases and/or condensates may emerge. They include the magnetic CFL (MCFL) phase that becomes relevant for fields of the order of the gap scale; the paramagnetic CFL, important when the field is of the order of the Meissner mass, and a spin-one condensate associated to the magnetic moment of the Cooper pairs, significant at fields of the order of the chemical potential. We discuss the equation of state (EoS) of MCFL matter for a large range of field values and consider possible applications of the magnetic effects on dense quark matter to the astrophysics of compact stars.
TL;DR: Analogous spacetimes have attracted significant and increasing attention over the last decade and a half as mentioned in this paper, and they provide general relativists with extremely concrete physical models to focus their thinking, and conversely the techniques of curved spacetime can sometimes help improve our understanding of condensed matter and/or optical systems by providing an unexpected and countervailing viewpoint.
Abstract: Analogue spacetimes (and more boldly, analogue models both of and for gravity), have attracted significant and increasing attention over the last decade and a half. Perhaps the most straightforward physical example, which serves as a template for most of the others, is Bill Unruh’s model for a dumb hole,(mute black hole, acoustic black hole), wherein sound is dragged along by a moving fluid—and can even be trapped behind an acoustic horizon. This and related analogue models for curved spacetimes are useful in many ways: analogue spacetimes provide general relativists with extremely concrete physical models to help focus their thinking, and conversely the techniques of curved spacetime can sometimes help improve our understanding of condensed matter and/or optical systems by providing an unexpected and countervailing viewpoint. In this chapter, I shall provide a few simple examples of analogue spacetimes as general background for the rest of the contributions.
TL;DR: In this article, it was shown that the quantum vacuum can become an electromagnetic superconductor in the presence of a strong external magnetic field of the order of 1016 Tesla, and that the superconducting properties of the new phase appear as a result of a magnetic-field-assisted condensation of quark-antiquark pairs with quantum numbers of electrically charged ρ ± mesons.
Abstract: The quantum vacuum may become an electromagnetic superconductor in the presence of a strong external magnetic field of the order of 1016 Tesla. The magnetic field of the required strength (and even stronger) are expected to be generated for very short times in ultraperipheral collisions of lead ions at the Large Hadron Collider. The superconducting properties of the new phase appear as a result of a magnetic-field-assisted condensation of quark–antiquark pairs with quantum numbers of electrically charged ρ ± mesons. We discuss similarities and differences between the suggested superconducting state of the quantum vacuum, a conventional superconductivity and the Schwinger pair creation. We argue qualitatively and quantitatively why the superconducting state should be a natural ground state of the vacuum at the sufficiently strong magnetic field. We demonstrate the existence of the superconducting phase using both the Nambu–Jona-Lasinio model and an effective bosonic model based vector meson dominance (the ρ-meson electrodynamics). We discuss various properties of the new phase such as absence of Meissner effect, anisotropy of superconductivity, spatial inhomogeneity of ground state, emergence of a neutral superfluid component in the ground state and presence of new topological vortices in the quark–antiquark condensates.
TL;DR: In this paper, the authors investigated the quantum critical behavior of strongly coupled 4-dimensional gauge theories in the presence of an external magnetic field, and finite charge density, including a nonzero charge density revealing a quantum critical point when the magnetic field reaches a critical value whose scale is set by the charge density.
Abstract: Holographic methods are used to investigate the low temperature limit, including quantum critical behavior, of strongly coupled 4-dimensional gauge theories in the presence of an external magnetic field, and finite charge density. In addition to the metric, the dual gravity theory contains a Maxwell field with Chern-Simons coupling. In the absence of charge, the magnetic field induces an RG flow to an infrared \(\mathit{AdS}_{3} \times {\bf R}^{2}\) geometry, which is dual to a 2-dimensional CFT representing strongly interacting fermions in the lowest Landau level. Two asymptotic Virasoro algebras and one chiral Kac-Moody algebra arise as emergent symmetries in the IR. Including a nonzero charge density reveals a quantum critical point when the magnetic field reaches a critical value whose scale is set by the charge density. The critical theory is probed by the study of long-distance correlation functions of the boundary stress tensor and current. All quantities of major physical interest in this system, such as critical exponents and scaling functions, can be computed analytically. We also study an asymptotically AdS 6 system whose magnetic field induced quantum critical point is governed by an IR Lifshitz geometry, holographically dual to a D=2+1 field theory. The behavior of these holographic theories shares important similarities with that of real world quantum critical systems obtained by tuning a magnetic field, and may be relevant to materials such as Strontium Ruthenates.
TL;DR: In this article, the authors give an elementary derivation of the chiral magnetic effect based on a strong magnetic field lowest-Landau-level projection in conjunction with axial anomalies in two-and four-dimensional space-time.
Abstract: We give an elementary derivation of the chiral magnetic effect based on a strong magnetic field lowest-Landau-level projection in conjunction with the well-known axial anomalies in two- and four-dimensional space-time. The argument is general, based on a Schur decomposition of the Dirac operator. In the dimensionally reduced theory, the chiral magnetic effect is directly related to the relativistic form of the Peierls instability, leading to a spiral form of the condensate, the chiral magnetic spiral. We then discuss the competition between spin projection, due to a strong magnetic field, and chirality projection, due to an instanton, for light fermions in QCD and QED. The resulting asymmetric distortion of the zero modes and near-zero modes is another aspect of the chiral magnetic effect.
TL;DR: In this article, an interdisciplinary review of the generalized Cerenkov emission of radiation from uniformly moving sources in the different contexts of classical electromagnetism, superfluid hydrodynamics, and classical hydroynamics is presented.
Abstract: We present an interdisciplinary review of the generalized Cerenkov emission of radiation from uniformly moving sources in the different contexts of classical electromagnetism, superfluid hydrodynamics, and classical hydrodynamics. The details of each specific physical systems enter our theory via the dispersion law of the excitations. A geometrical recipe to obtain the emission patterns in both real and wave-vector space from the geometrical shape of the dispersion law is discussed and applied to a number of cases of current experimental interest. Some consequences of these emission processes onto the stability of condensed-matter analogues of gravitational systems are finally illustrated.
TL;DR: In this paper, the authors introduce the fundamentals of black hole geometry, the thermality of the vacuum, and the Hawking effect in spacetime and its analogues, and discuss the effects of these properties on the trans-planckian question, short wavelength dispersion, and white hole radiation.
Abstract: These notes introduce the fundamentals of black hole geometry, the thermality of the vacuum, and the Hawking effect, in spacetime and its analogues. Stimulated emission of Hawking radiation, the trans-Planckian question, short wavelength dispersion, and white hole radiation in the setting of analogue models are also discussed. No prior knowledge of differential geometry, general relativity, or quantum field theory in curved spacetime is assumed. The discussion attempts to capture the essence of these topics without oversimplification.
TL;DR: In this article, the D3-D7 and D4-D8 models were discussed, where the probe branes were incorporated into the gravitational background dual to the gauge theory.
Abstract: Gauge/gravity duality is a useful and efficient tool for addressing and studying questions related to strongly interacting systems described by a gauge theory. In this manuscript we will review a number of interesting phenomena that occur in such systems when a background magnetic field is turned on. Specifically, we will discuss holographic models for systems that include matter fields in the fundamental representation of the gauge group, which are incorporated by adding probe branes into the gravitational background dual to the gauge theory. We include three models in this review: the D3–D7 and D4–D8 models, that describe four-dimensional systems, and the D3–D7’ model, that describes three-dimensional fermions interacting with a four-dimensional gauge field.
TL;DR: In this article, a time-series of six circularly polarized spectra was obtained using the NARVAL spectropolarimeter at Telescope Bernard Lyot (Pic du Midi Observatory (F)), between March and April 2010.
Abstract: We present the outcome of a highly-sensitive search for magnetic fields on the cool supergiant Betelgeuse. A time-series of six circularly polarized spectra was obtained using the NARVAL spectropolarimeter at Telescope Bernard Lyot (Pic du Midi Observatory (F)), between March and April 2010. Zeeman signatures were repeatedly detected in cross-correlation profiles, corresponding to a longitudinal component of about 1 G. The time-series unveils a smooth increase of the longitudinal field from 0.5 to 1.5 G, correlated with radial velocity fluctuations. We observe a strong asymmetry of Stokes V signatures, also varying in correlation with the radial velocity. The Stokes V line profiles are red-shifted by about 9 km s−1 with respect to the Stokes I profiles, suggesting that the observed magnetic elements may be concentrated in the sinking components of the convective flows.