1,720,982 research outputs found
Drag suppression in anomalous chiral media
No full textWe study a heavy impurity moving longitudinal with the direction of an external magnetic field in an anomalous chiral medium. Such system would carry a nondissipative current of chiral magnetic effect associated with the anomaly. We show, by generalizing Landau’s criterion for superfluidity, that the “anomalous component” which gives rise to the anomalous transport will not contribute to the drag experienced by an impurity. We argue on a very general basis that those systems with a strong magnetic field would exhibit an interesting transport phenomenon—the motion of the heavy impurity is frictionless, in analogy to the case of a superfluid. We demonstrate and confirm our general results with two complementary examples: weakly coupled chiral fermion gases and strongly interacting chiral liquids.Russian Science Foundation (Grant No 16-12- 10059)United States. Department of Energy (Contract No. DE-SC0011090
Chiral anomalous dispersion
Get PDFThe linearized Einstein equation describing graviton propagation through a chiral medium appears to be helicity dependent. We analyze features of the corresponding spectrum in a collision-less regime above a flat background. In the long wave-length limit, circularly polarized metric perturbations travel with a helicity dependent group velocity that can turn negative giving rise to a new type of an anomalous dispersion. We further show that this chiral anomalous dispersion is a general feature of polarized modes propagating through chiral plasmas extending our result to the electromagnetic sector. Keywords: Anomalies in Field and String Theories; Thermal Field TheoryUnited States. Department of Energy (Contract DE-SC0011090
The charmonium dissociation in an “anomalous wind”
Get PDFWe study the charmonium dissociation in a strongly coupled chiral plasma in the presence of magnetic field and axial charge imbalance. This type of plasma carries “anomalous flow” induced by the chiral anomaly and exhibits novel transport phenomena such as chiral magnetic effect. We found that the “anomalous flow” would modify the charmonium color screening length by using the gauge/gravity correspondence. We derive an analytical expression quantifying the “anomalous flow” experienced by a charmonium for a large class of chiral plasma with a gravity dual. We elaborate on the similarity and qualitative difference between anomalous effects on the charmonium color screening length which are model-dependent and those on the heavy quark drag force which are fixed by the second law of thermodynamics. We speculate on the possible charmonium dissociation induced by the chiral anomaly in heavy ion collisions.United States. Department of Energy (Contract No. DE-SC0011090
Chiral vortical effect for bosons
No full textThe thermal contribution to the chiral vortical effect is believed to be related to the axial anomaly in external gravitational fields. We use the universality of the spin-gravity interaction to extend this idea to a wider set of phenomena. We consider the Kubo formula at weak coupling for the spin current of a vector field and derive a novel anomalous effect caused by the medium rotation: the chiral vortical effect for bosons. The effect consists in a spin current of vector bosons along the angular velocity of the medium. We argue that it has the same anomalous nature as in the fermionic case and show that this effect provides a mechanism for helicity transfer, from flow helicity to magnetic helicity.United States. Department of Energy (Contract DE-SC0011090
Evolution of the Jet Opening Angle Distribution in Holographic Plasma
No full textWe use holography to analyze the evolution of an ensemble of jets, with an initial probability distribution for their energy and opening angle as in proton-proton (pp) collisions, as they propagate through an expanding cooling droplet of strongly coupled plasma as in heavy ion collisions. We identify two competing effects: (i) each individual jet widens as it propagates and (ii) because wide-angle jets lose more energy, energy loss combined with the steeply falling perturbative spectrum serves to filter wide jets out of the ensemble at any given energy. Even though every jet widens, jets with a given energy can have a smaller mean opening angle after passage through the plasma than jets with that energy would have had in vacuum, as experimental data may indicate. .United States. Department of Energy (Grant DE-SC0011090
Chiral drag force
Get PDFWe provide a holographic evaluation of novel contributions to the drag force acting on a heavy quark moving through strongly interacting plasma. The new contributions are chiral in the sense that they act in opposite directions in plasmas containing an excess of left- or right-handed quarks. The new contributions are proportional to the coefficient of the axial anomaly, and in this sense also are chiral. These new contributions to the drag force act either parallel to or antiparallel to an external magnetic field or to the vorticity of the fluid plasma. In all these respects, these contributions to the drag force felt by a heavy quark are analogous to the chiral magnetic effect (CME) on light quarks. However, the new contribution to the drag force is independent of the electric charge of the heavy quark and is the same for heavy quarks and antiquarks, meaning that these novel effects do not in fact contribute to the CME current. We show that although the chiral drag force can be non-vanishing for heavy quarks that are at rest in the local fluid rest frame, it does vanish for heavy quarks that are at rest in a suitably chosen frame. In this frame, the heavy quark at rest sees counterpropagating momentum and charge currents, both proportional to the axial anomaly coefficient, but feels no drag force. This provides strong concrete evidence for the absence of dissipation in chiral transport, something that has been predicted previously via consideration of symmetries. Along the way to our principal results, we provide a general calculation of the corrections to the drag force due to the presence of gradients in the flowing fluid in the presence of a nonzero chemical potential. We close with a consequence of our result that is at least in principle observable in heavy ion collisions, namely an anticorrelation between the direction of the CME current for light quarks in a given event and the direction of the kick given to the momentum of all the heavy quarks and antiquarks in that event.United States. Department of Energy (Contract Number DE-SC0011090)Russian Foundation for Basic Research (grant 14-02-01185A
Anomalous transport and generalized axial charge
Get PDFIn this paper we continue studying the modification of the axial charge in chiral media by macroscopic helicities. Recently it was shown that magnetic reconnections result in a persistent current of zero mode along flux tubes. Here we argue that in general a change in the helical part of the generalized axial charge results in the same phenomenon. Thus one may say that there is a novel realization of chiral effects requiring no initial chiral asymmetry. The transfer of flow helicity to zero modes is analyzed in a toy model based on a vortex reconnection in a chiral superfluid. Then, we discuss the balance between the two competing processes effect of reconnections and the chiral instability on the example of magnetic helicity. We argue that in the general case there is a possibility for the distribution of the axial charge between the magnetic and fermionic forms at the end of the instability.United States. Department of Energy (Contract DE-SC0011090
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
High energy probes of the initial stages
No full textThe matter produced in heavy-ion collisions undergoes a multiphase evolution, providing unique access to a variety of QCD matter properties. Hard probes, which penetrate the medium and carry away imprints of different phases, serve as a key tool for studying this evolution. While their interaction with the medium in the very first moments after a collision was historically assumed to be negligible, recent studies suggest otherwise. In this talk, I will review how hard probes interact with nuclear matter from the earliest stages of a heavy-ion collision onward. Using jets as an example, I will discuss how they lose energy and how their substructure is modified during the pre-equilibrium phases, comparing these effects with their interactions in the later quark-gluon plasma stage. Understanding these early-time interactions provides new insights into the thermalization process and the microscopic structure of the QCD medium
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