arXiv subjects

Edward Shuryak

Publications and source records attributed to Edward Shuryak.

At least 145 records · Page 8Linked to original sources

arXiv2009

Magnetic Scenario for the QCD Fluid at RHIC

We present new developments of the "magnetic scenario" for the QCD Fluid observed at RHIC. The recent lattice data for finite T monopoles are used to pin down the parameters of the magnetic component of quark-gluon plasma: in particular we show how the magnetic density and plasma coupling $Γ_M$ change with $T$. We then discuss one central issue imposed by the heavy ion data: i.e. the extremely short dissipation length in the QCD fluid around $T_c$. We show that the Lorentz trapping effect, present only in a plasma with both electric and magnetic charges and maximal for an equal 50%-50% mixture, is the microscopic mechanism leading to the nearly perfect fluidity.

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arXiv2009

Angular Dependence of Jet Quenching Indicates Its Strong Enhancement Near the QCD Phase Transition

We study dependence of jet quenching on matter density, using "tomography" of the fireball provided by RHIC data on azimuthal anisotropy $v_2$ of high $p_t$ hadron yield at different centralities. Slicing the fireball into shells with constant (entropy) density, we derive a "layer-wise geometrical limit" $v_2^{max}$ which is indeed above the data $v_2 T_c$. One possible reason for that may be recent indications that the near-$T_c$ region is a magnetic plasma of relatively light color-magnetic monopoles.

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arXiv2009

Toward the AdS/CFT Gravity Dual for High Energy Collisions. 3.Gravitationally Collapsing Shell and Quasiequilibrium

The equilibration of matter and onset of hydrodynamics can be understood in the AdS/CFT context as a gravitational collapse process, in which "collision debris" create a horizon. In this paper we consider the simplest geometry possible, a flat shell (or membrane) falling in the holographic direction toward the horizon. The metric is a combination of two well known solutions: thermal AdS above the shell and pure AdS below, while motion of the shell is given by the Israel junction condition. Furthermore, when the shell motion can be considered slow, we were able to solve for two-point functions of all boundary stress tensor and found that an observer on the boundary sees a very peculiar $quasiequilibrium$: while the average stress tensor $ }$ contains the equilibrium plasma energy and pressure at all times, the spectral densities of the correlators(related with occupation probabilities of the modes) reveal additional oscillating terms absent in equilibrium. This is explained by the "echo" phenomenon, a partial return of the field coherence at certain "echo" times.

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arXiv2009

Grazing Collisions of Gravitational Shock Waves and Entropy Production in Heavy Ion Collision

AdS/CFT correspondence is now widely used for study of strongly coupled plasmas, such as produced in ultrarelativistic heavy ion collisions at RHIC. While properties of equilibrated plasma and small deviations from equilibrium are by now reasonably well understood, its initial formation and thermal equilibration is much more challenging issue which remains to be studied. In the dual gravity language, these problems are related to formation of bulk black holes, and trapped surfaces we study in this work is a way to estimate the properties (temperature and entropy) of such black hole. Extending the work by Gubser et al, we find numerically trapped surfaces for non-central collision of shock waves with different energies. We observe a critical impact parameter, beyond which the trapped surface does not exist: and we argue that there are experimental indications for similar critical impact parameter in real collisions. We also present a simple solvable example of shock wave collision: wall-on-wall collision. The applicability of this approach to heavy ion collision is critically discussed.

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arXiv2008

The role of monopoles in a Gluon Plasma

We study the role of magnetic monopoles at high enough temperature $T>2T_c$, when they can be considered heavy, rare objects embedded into matter consisting mostly of the usual "electric" quasiparticles, quarks and gluons. We review available lattice results on monopoles at finite temperatures. Then we proceed to classical and quantum charge-monopole scattering, solving the problem of gluon-monopole scattering for the first time. We find that, while this process hardly influences thermodynamic quantities, it does produce a large transport cross section, significantly exceeding that for pQCD gluon-gluon scattering up to quite high $T$. Thus, in spite of their relatively small density at high $T$, monopoles are extremely important for QGP transport properties, keeping viscosity small enough for hydrodynamics to work at LHC.

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arXiv2008

Light bound states of heavy fermions

In the Standard Model, a group of heavy fermions, e.g. top quarks, can collectively strongly affect the Higgs field and create relatively long-lived bound states. If there exist new generations of fermions with masses beyond 1 TeV, strong binding of several of them can make them lighter than even a single heavy fermion. Using the mean field approximation we find multi-fermion states with masses M ~ 5 v N^{1/2} ~ 1.2 N^{1/2} TeV, with N=2,3... being the total number of heavy fermions bound together, and v=246 GeV the Higgs VEV. The experimental search for multi-fermions within the range of energies 2-3 Tev would either discover them, or suggest absence of new Standard Model fermions with larger masses. Possible implications related to multi-top states and baryonic asymmetry of the Universe are discussed.

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arXiv2008

Charmonium in strongly coupled quark-gluon plasma

The growing consensus that a strongly-coupled quark-gluon plasma (sQGP) has been observed at the SPS and RHIC experiments suggests a different framework for examining heavy quark dynamics. We present both semi-analytical treatment of Fokker-Planck (FP) evolution in pedagogical examples and numerical Langevin simulations of evolving charm quark-antiquark pairs on top of a hydrodynamically expanding fireball. In this way, we may conclude that the survival probability of bound charmonia states is greater than previously estimated, as the spatial equilibration of pairs proceeds through a ``slowly dissolving lump'' stage related to the pair interaction.

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arXiv2008

Physics of Strongly coupled Quark-Gluon Plasma

This review cover our current understanding of strongly coupled Quark-Gluon Plasma (sQGP), especially theoretical progress in (i) explaining the RHIC data by hydrodynamics, (ii) describing lattice data using electric-magnetic duality; (iii) understanding of gauge-string duality known as AdS/CFT and its application for "conformal" plasma. In view of interdisciplinary nature of the subject, we include brief introduction into several topics "for pedestrians". Some fundamental questions addressed are: Why is sQGP such a good liquid? What is the nature of (de)confinement and what do we know about ''magnetic'' objects creating it? Do they play any important role in sQGP physics? Can we understand the AdS/CFT predictions, from the gauge theory side? Can they be tested experimentally? Can AdS/CFT duality help us understand rapid equilibration/entropy production? Can we work out a complete dynamical "gravity dual" to heavy ion collisions?

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arXiv2008

Magnetic Component of Quark-Gluon Plasma is also a Liquid!

The so called magnetic scenario recently suggested in \cite{Liao_ES_mono} emphasizes the role of monopoles in strongly coupled quark-gluon plasma (sQGP) near/above the deconfinement temperature, and specifically predicts that they help reduce its viscosity by the so called "magnetic bottle" effect. Arguments for "magnetic liquid" in 1-2$T_c$ based on lattice measurement of monopole density were provided in \cite{Chernodub}. Here we present results for monopole-(anti)monopole correlation functions from the same classical molecular dynamics simulations, which are found to be in very good agreement with recent lattice results \cite{D'Alessandro:2007su}. We show that the magnetic Coulomb coupling does run in the direction $opposite$ to the electric one, as expected, and it is roughly inverse of the asymptotic freedom formula for the electric one. However, as $T$ decreases to $T_c$, the magnetic coupling never gets weak, with the plasma parameter always large enough ($Γ>1$). This nicely agrees with empirical evidences from RHIC experiments, implying that magnetic objects cannot have large mean free path and should also form a good liquid with low viscosity.

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arXiv2008

On bound states of multiple t-quarks due to Higgs exchange

Froggatt, Nielsen et al suggested that the Higgs boson exchange between top quarks produces enough attraction to generate their multiple bound states. Furthermore they claimed that the system of 6 top and 6 anti-top quarks is bound so strongly that the binding energy nearly compensates the masses of t-quarks, making it very light. We calculated the energy of such states more accurately, variationally and by self-consistent mean field approximation, and found that these state are weakly bound for massless Higgs boson and unbound with the account for its mass.

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arXiv2008

Toward the AdS/CFT gravity dual for High Energy Collisions: I.Falling into the AdS

In the context of the AdS/CFT correspondence we discuss the gravity dual of a high energy collision in a strongly coupled ${\cal N}=4$ SYM gauge theory. We suggest a setting in which two colliding objects are made of non-dynamical heavy quarks and antiquarks, which allows to treat the process in classical string approximation. Collision ``debris'' consist of closed as well as open strings. If the latter have ends on two outgoing charges, and thus are being ``stretched'' along the collision axes. We discuss motion in AdS of some simple objects first -- massless and massive particles -- and then focus on open strings. We study the latter in a considerable detail, concluding that they rapidly become ``rectangular'' in proper time -spatial rapidity $τ-y$ coordinates with well separated fragmentation part and a near-free-falling rapidity-independent central part. Assuming that in the collisions of ``walls'' of charges multiple stretching strings are created, we also consider the motion of a 3d stretching membrane. We then argue that a complete solution can be approximated by two different vacuum solutions of Einstein eqns, with matter membrane separating them. We identify one of this solution with Janik-Peschanski stretching black hole solution, and show that all objects approach its (retreating) horizon in an universal manner.

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arXiv2008

Toward the AdS/CFT Gravity Dual for High Energy Collisions: II. The Stress Tensor on the Boundary

In this second paper of the series we calculate the stress tensor of excited matter, created by ``debris'' of high energy collisions at the boundary. We found that massive objects (``stones'') falling into the AdS center produce gravitational disturbance which however has $zero$ stress tensor at the boundary. The falling open strings, connected to receeding charges, do produce a nonzero stress tensor which we found analytically from time-dependent linearized Einstein equations in the bulk. It corresponds to exploding non-equilibrium matter: we discuss its behavior in some detail, including its internal energy density in a comoving frame and the ``freezeout surfaces''. We then discuss what happens for the ensemble of strings.

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arXiv2008

Magnetic Component of Quark-Gluon Plasma

We describe recent developments of the "magnetic scenario" of sQGP. We show that at $T=(0.8-1.3)T_c$ there is a dense plasma of monopoles, capable of supporting metastable flux tubes. Their existence allows to quantitatively explained the non-trivial $T$-dependence of the static $\bar Q Q$ potential energy calculated on the lattice. By molecular dynamics simulation we derived transport properties (shear viscosity and diffusion constant) and showed that the best liquid is given by most symmetric plasma, with 50%-50% of electric and magnetic charges. The results are close to those of the ``perfect liquid'' observed at RHIC.

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arXiv2008

Quark-Gluon Plasma - New Frontiers

As implied by organizers, this talk is not a conference summary but rather an outline of progress/challenges/``frontiers'' of the theory. Some fundamental questions addressed are: Why is sQGP such a good liquid? Do we understand (de)confinement and what do we know about ``magnetic'' objects creating it? Can we understand the AdS/CFT predictions, from the gauge theory side? Can they be tested experimentally? Can AdS/CFT duality help us understand rapid equilibration/entropy production? Can we work out a complete dynamical ``gravity dual'' to heavy ion collisions?

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arXiv2007

A "Domain Wall" Scenario for the AdS/QCD

We propose a scenario for bottom-up gravity dual picture of QCD-like theories, which consists of two near-AdS$_5$ domains separated by the ``domain wall'' at which the effective coupling relatively rapidly switches from small perturbative value at its UV side to strong at its IR side. Its consequence are corresponding jumps in 5-d masses of the bulk fields, related to different anomalous dimensions of the corresponding operators. Inclusion of both weakly and strongly coupled parts of bulk wave functions allows for consistent inclusion of QCD hard processes. We further discuss how transitions from strong to weak coupling in hard observables should look like, exemplified by pion diffractive dissociation, which seems to show this transition experimentally. Then we propose a dynamical mechanism for this jump related to instantons, which are point-like bulk objects located at/near the domain wall. We further argue that in the limit of large number of colors $N_c\to\infty$ the "domain wall" is becoming a true singularity. Instanton-induced contributions to correlators and partition function of the instanton ensemble is reformulated in the $AdS_5$ language. Among other applications are lowest mesons as collective vibrations of the ``domain wall''.

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arXiv2007

Electric Flux Tube in Magnetic Plasma

In this paper we study a methodical problem related to the magnetic scenario recently suggested and initiated by the authors \cite{Liao_ES_mono} to understand the strongly coupled quark-gluon plasma (sQGP): the electric flux tube in monopole plasma. A macroscopic approach, interpolating between Bose condensed (dual superconductor) and classical gas medium is developed first. Then we work out a microscopic approach based on detailed quantum mechanical calculation of the monopole scattering on electric flux tube, evaluating induced currents for all partial waves. As expected, the flux tube looses its stability when particles can penetrate it: we make this condition precise by calculating the critical value for the product of the flux tube size times the particle momentum, above which the flux tube dissolves. Lattice static potentials indicate that flux tubes seem to dissolve at $T>T_{dissolution} \approx 1.3 T_c$. Using our criterion one gets an estimate of the magnetic density $n\approx 4.4 \sim 6.6 fm^{-3}$ at this temperature.

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arXiv2007

Electric-Magnetic Struggle in QGP, Deconfinement and Baryons

We argue that quite unusual properties of Quark-Gluon Plasma in the RHIC temperature domain $T=(1-2)T_c$ are consequences of the approximate equilibrium between electric and magnetic sectors reached above the deconfinement temperature. Already classical study of few body motion in a electric-magnetic plasma shows abnormally large scattering rate due to the so called ``magnetic bottle'' effect. Molecular dynamics simulation have found that equal mixture of electric and magnetic quasiparticles do produce plasmas of small viscosity and even smaller diffusion rate, comparable to what is needed to explain RHIC data and also to what follows from AdS/CFT. As a separate issue, we point out that right above $T_c$ there should be surviving s-wave baryons made of quarks ($N,Δ$), as well as adjoint objects, 3-gluon and 3-monopole chains (the latter being nothing else but ``calorons'' or finite-T instantons).

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arXiv2007

Stress Tensor of Static Dipoles in strongly coupled $\cal{N}$=4 Gauge Theory

In the context of the AdS/CFT correspondence we calculate the induced stress tensor of static dipoles (electric-electric and electric-magnetic) in a strongly coupled ${\cal N}=4$ SYM gauge theory, by solving the linearized Einstein equation with Maldecena string as a source. Analytic expressions are given for the far-field and a near-field close to one charge, and compared to what one has in weak coupling. The result can be compared to lattice results for QCD-like theories in a deconfined but strongly coupled regime.

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