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This paper attempts to answer some frequently asked questions (FAQS) about Quarkyonic Matter.

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I present a brief review of recent phenomenological analyses of HERA, RHIC and LHC data based on the Color Glass Condensate, including the use of non-linear evolution equations with running coupling.

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We discuss the production of forward jets in high energy processes where one probes a dense hadronic wavefunction. In particular, and as a signature of parton saturation, we discuss the possibility of a strong momentum decorrelation in Mueller–Navelet jets which leads to a geometric scaling behavior.

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This talk discusses a recent approach developed to deduce the existence of a Hagedorn spectrum — that is a hadron spectrum in which the number of hadrons grows exponentially with mass — from QCD. The approach is valid in the large \(N_c\) limit of QCD and exploits a tension between asymptotic freedom and confinement. While the approach is not rigorous in the sense of a mathematical theorem, it will hold provided certain standard assumptions made about correlation function in QCD are correct.

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The linear \(\sigma \)-model has been widely used to describe the chiral phase transition. Numerically, the critical temperature \(T_{\rm c}\) of the chiral phase transition is in agreement with other effective theories of QCD. However, in the large-\(N_{c}\) limit \(T_{\rm c}\) scales as \(\sqrt {N_{c}}\) which is not in line with the NJL model and with basic expectations of QCD, according to which \(T_{\rm c}\) is — just as the deconfinement phase transition — \(N_{c}\)-independent. This mismatch can be corrected by a phenomenologically motivated temperature dependent parameter.

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The mass spectrum of pure Yang–Mills theory in \(3+1\) dimensions is discussed for an arbitrary simple gauge algebra within a quasigluon picture. The general structure of the low-lying gluelump and glueball spectrum is shown to be common to all algebras, excepted the lightest \(C=-\) glueballs that only exist when the gauge algebra is \(A_{r\geq 2}\). The shape of the static energy between adjoint sources is also discussed assuming the Casimir scaling hypothesis and finally, the obtained results are shown to be consistent with existing lattice data in the large-\(N\) limit of an \(\mathfrak {su}(N)\) gauge algebra.

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In this paper, we report on the results from ALICE during the first Pb–Pb data taking period at the CERN LHC. We present the centrality dependence of the multiplicity density at mid-rapidity, the first results on Bose–Einstein correlations, the first elliptic flow measurements as well as the studies related to the suppression of high \(p_{\rm T}\) particles in central collisions (\(R_{AA}\)).

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Results from a variety of QCD and Heavy Ion physics analyses are presented using \(pp\) and PbPb collision data collected by the CMS experiment at \(\sqrt {s}=7\) TeV and 2.76 TeV, respectively. The data distributions are compared with the predictions of Monte Carlo event generators and with perturbative QCD calculations.

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Lowering the string scale in the TeV region provides a theoretical framework for solving the mass hierarchy problem and unifying all interactions. The apparent weakness of gravity can then be accounted by the existence of large internal dimensions, in the submillimeter region, and transverse to a braneworld where our Universe must be confined. I review the main properties of this scenario and its experimental implications.

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The QCD transition is studied on lattices up to \(N_t=16\). The chiral condensate is presented as a function of temperature, and the corresponding transition temperature is extracted. The equation of state is determined on lattices with \(N_t=6\), 8, 10 and at some temperature values with \(N_t=12\). The pressure and the trace anomaly are presented as functions of the temperature in the range 100–1000 MeV. Using the same configurations we determine the continuum extrapolated phase diagram of QCD on the \(\mu \)–\(T\) plane for small to moderate chemical potentials. Two transition lines are defined with two quantities, the chiral condensate and the strange quark number susceptibility.

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Novel nonperturbative properties of QED in three dimensions are examined at finite temperature. We show that infrared divergences are endemic to the theory and discuss difficulties in computing the electric screening mass.

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We give a general overview about the approaches to study the phase diagram of QCD. Thereafter, we examine the evolution of a fireball in a chiral fluid dynamic model including nonequilibrium effects.

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Many of the earliest ATLAS results based on 2010 LHC data are focused on strong interaction dynamics. This contribution reports on a selection of these results, including minimum bias observables, hard scattering cross-sections and the first heavy ion collision data.

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We report on recent studies of the phenomenon of color decoherence of jets in QCD media. The effect is most clearly observed in the radiation pattern of a quark–antiquark antenna, created in the same quantum state, traversing a dense color deconfined plasma. Multiple scattering with the medium color charges gradually destroys the coherence of the antenna. In the limit of opaque media this ultimately leads to independent radiation off the antenna constituents. Accordingly, radiation off the total charge vanishes implying a memory loss effect induced by the medium.

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We discuss recent developments in the EPOS approach, concerning an event-by-event treatment of the hydrodynamical evolution in heavy ion collisions and also in high multiplicity \(pp\) scatterings at the LHC. The initial conditions are flux-tubes, which are formed following elementary (multiple) scatterings. We show that this picture leads in a natural way to the so-called ridge structures, observed in heavy ion and proton–proton collisions.

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Dilepton production has been proposed as one of the most promising observables to study QCD matter at extreme conditions. We review some of the main theoretical and experimental results of dilepton production in ultrarelativistic heavy ion collisions. We concentrate on dilepton emission from partonic as well as from the hadronic sources. We briefly comment about the status of theoretical calculations compared with available experimental data.

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In this paper, I reflect on the physical origin of the strongly coupled character of the quark-gluon plasma.

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In this paper, we briefly review the current understanding of the behavior of the QCD equation of state throughout the phase diagram. Special emphasis is given to regions of phenomenological interest, and a number of important open questions as well as directions of ongoing research are pointed out. These include in particular the region of low temperatures and (moderately) high densities, where at the moment we have extremely few first principles tools available.

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We present a study of the heavy-flavor dynamics in nucleus–nucleus collisions. The initial (hard) production of \(c\) and \(b\) quarks is taken from NLO pQCD predictions. The presence of a hot medium (a Quark-Gluon Plasma described by hydrodynamics) affects the final spectra of open-charm (beauty) hadrons and their decay electrons with respect to what found in \(pp\) collisions. The propagation of \(c\) and \(b\) quarks in the plasma is based on a picture of multiple uncorrelated random collisions, described by a relativistic Langevin equation. A microscopic evaluation of the transport coefficients is provided within a pQCD approach (with proper resummation of medium effects). Results for the final spectra of heavy-flavor hadrons and decay-electrons are given, with particular emphasis on \(R_{AA}\) and \(v_2\).

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In the context of the AdS/CFT holographic correspondence, the thermodynamics of the deconfined phase of four-dimensional gauge theories is mapped to the thermodynamics of higher-dimensional black hole solutions of a dual gravity model. Here, I review the basic ingredients of the correspondence, and how one can construct simple semi-realistic holographic models that give a quantitatively good description of Yang–Mills thermodynamics.

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We study the effect of a constant external magnetic field on the rho meson mass \(m_\rho \) on the one hand, and on the chiral symmetry restoration temperature \(T_\chi \) on the other hand, using the Sakai–Sugimoto model with two quenched flavours and non-zero constituent quark masses, which is a holographic dual of a QCD-like theory in the quenched approximation and chiral limit. We find that the explicit chiral symmetry breaking caused by the presence of the magnetic field \(eB\) manifests itself in a stronger chiral magnetic catalysis effect for the up than for the down quarks, resulting in two separate chiral symmetry restoration temperatures \(T_\chi ^u\) and \(T_\chi ^d\), with \(T_\chi ^u(eB) \gt T_\chi ^d(eB) \gt T_{\rm c}\) (the deconfinement temperature) for each value of \(eB\). The Landau levels described in the rho meson mass equation indicate an instability of the QCD vacuum towards condensation of rho mesons at \(eB \sim 1.1 \, m_\rho ^2 \approx 0.67\) GeV\(^2\), confirming a recent prediction of Chernodub.

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The main features of the glueball spectrum is discussed.

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The U\(_{\rm A}(1)\) properties of the three-quark nucleon interpolating fields have recently been used to predict the flavor-singlet (isoscalar) axial coupling of the nucleon (“the spin problem”) based on chiral mixing, with \(F\) and \(D\) values as input, or vice versa, in reasonable agreement with experiment. Here, we derive such mixing from effective chiral Lagrangians: first we construct all SU\(_{\rm L}(3) \times {\rm SU}_{\rm R}(3)\) chirally invariant non-derivative one-meson–baryon interactions and then we calculate the mixing angles in terms of baryons’ masses. It turns out that these Lagrangians are subject to (strong) chiral selection rules. For example, there is only one non-derivative chirally symmetric interaction between \(J=\frac 12\) fields belonging to the \([({6},{3})\oplus ({3},{6})]\) and the \([({3}, \overline {{3}}) \oplus (\overline {{3}}, {\bf 3})]\) chiral multiplets, that is also U\(_{\rm A}(1)\) symmetric. We use these Lagrangians to fit the mixing angles by choosing the two lowest lying observed nucleon (resonance) masses, and then predict the third \((J=\frac 12, I=\frac 32)\) \({\mit \Delta }\) resonance, as well as one or two flavor-singlet \({\mit \Lambda }\) hyperon(s), in agreement with particle data group tables.

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Tetraquarks are studied with an approximation which reduces the internal degrees of freedom of the system, using both finite differences and scattering theory. The existence of bound states and resonances is inspected and the masses and widths of the found resonances are calculated.

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Graphics Processing Units (GPUs) are being used in many areas of physics, since the performance versus cost is very attractive. The GPUs can be addressed by CUDA which is a NVIDIA’s parallel computing architecture. It enables dramatic increases in computing performance by harnessing the power of the GPU. We present a performance comparison between the GPU and CPU with single precision and double precision in generating lattice SU(2) configurations. Analyses with single and multiple GPUs, using CUDA and OPENMP, are also presented. We also present SU(2) results for the renormalized Polyakov loop, colour averaged free energy and the string tension as a function of the temperature.

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We discuss an effective theory for QCD at finite chemical potential and non-zero temperature, where QCD is reduced to its center degrees of freedom. The effective action can be mapped to a flux representation, where the complex phase problem is solved and the theory accessible to Monte Carlo techniques. In this work, we use a generalized Prokof’ev–Svistunov worm algorithm to perform the simulations and determine the phase diagram as a function of temperature, quark mass and chemical potential. It turns out that the transition is qualitatively as expected for QCD.

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Here, we overview a possible mechanism for confining but chirally symmetric matter at low temperatures and large densities.

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We briefly discuss the status of the signatures of the QCD critical endpoint in heavy-ion collisions concentrating on the role played by the finiteness of the medium created in such experiments.

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We apply strong-coupling expansion techniques to finite-temperature lattice pure gauge theory, obtaining dimensionally reduced \(Z_N\)-symmetric effective theories. The analytic mappings between the effective couplings and the original one, viz. \(\beta \), allows to estimate the transition point \(\beta _{\rm c}\) of the 4D theory for a large range of the imaginary-time extent \(N_\tau \) of the lattice. We study the models for SU\((3)\) via Monte Carlo simulation, finding satisfactory agreement with the critical point of the original theories especially at low \(N_\tau \).

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Features of the non-strange \(\bar n n\) and strange \(\bar s s\) scalar mesons are investigated in the Extended Linear Sigma Model (eLSM) with \(N_f=3\) and vector and axial-vector mesons. Our model contains a pure non-strange and a pure strange scalar state; implementing the mixing of the two states originates two new states, a predominantly non-strange and a predominantly strange one. We investigate the possibility to assign the two mixed states to experimentally well-established resonances. To this end, we calculate the masses and the two-pion decay widths of the mixed states and compare them with experimental data. The predominantly non-strange state is found to be consistent with the resonance \(f_0(1370)\) and the predominantly strange state with the resonance \(f_0(1710)\).

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The study of the O\((N)\) model at nonzero temperature is presented applying the auxiliary field method, which allows to obtain a continuous transformation between the linear and the nonlinear version of the model. In the case of explicitly broken chiral symmetry the order of the chiral phase transition changes from crossover to first order as the vacuum mass of the \(\sigma \) particle increases. In the chiral limit one observes a first order phase transition and the Goldstone’s theorem is fulfilled.

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We show how to resum perturbative series in both the one- and two-loop fractional analytic perturbation theory.

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The combined analysis of the pion-induced and photoproduction data reveals evidences for unknown nucleon resonances in the fourth resonance region. Two solutions with different pattern of high spin, positive parity states were found. Although the first solution shows a rather large mass gap between high spin baryons with positive and negative parities, the second solution supports the idea of chiral symmetry restoration at high energies. The new polarization data should provide a necessary information to distinguish these two solutions.

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I report on a lattice computation of the energy of a system of two light quarks and two static antiquarks as a function of the separation of the static antiquarks. In terms of hadrons such a system corresponds to a pair of \(B\) mesons and its energy to the hadronic potential. I present selected results for different isospin, spin and parity combinations of the individual \(B\) mesons mainly focusing on those channels relevant to determine, whether two \(B\) mesons may form a bound tetraquark state.

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We analyze the survival probability of unstable particles in the context of quantum field theory. After introducing the spectral function of resonances, we show that deviations from the exponential decay law occur at short times after the creation of the unstable particle. For hadronic decays, these deviations are sizable and could lead to observable effects.

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The energy loss of heavy quarks in the hot and dense matter created at RHIC can be used to probe the properties of the medium. Both charm and beauty quarks contribute to non-photonic electrons through their semi-leptonic decays. Thus it is essential to determine experimentally the relative contribution of those flavors for understanding the suppression of beauty at high \(p_{\rm T}\) in central Au + Au collisions. The azimuthal angular correlations of non-photonic electrons with the reconstructed \(D^{0}\) allow to disentangle that contribution. Furthermore, presence of a non-photonic electron significantly reduces the background in the \(D^{0}\) invariant mass region. In this paper the STAR measurement of a non-photonic electron and \(D^{0}\rightarrow K \pi \) azimuthal correlations in \(p+p\) collisions at 200 GeV will be presented along with perspectives on such measurement for the Au + Au system.

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The H1 and ZEUS Collaborations have measured the inclusive diffractive DIS cross-section \(ep \rightarrow eXp\) with very high precision across a wide kinematic range. Diffractive parton density functions (DPDFs) have been extracted from the data using the DGLAP evolution equations at next-to-leading-order (NLO) of perturbative QCD. Results from diffractive dijets in DIS have also been included in the fit. Exclusive diffractive vector meson (VM) production and deeply virtual Compton scattering (DVCS) have been studied, shedding light on the transition from the soft to the hard regime of strong interaction.

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We discuss exclusive production of lepton pairs via photon–photon fusion and photon–pomeron subprocesses. Predictions for this reactions are given using the \(k_{\rm t}\)-factorisation formalism. We also analyse inclusive diffractive dilepton production in \(pp\) collisions using Ingelman and Schlein approach with pomeron flux factors and quark/antiquark distributions in the pomeron which were taken from the H1 Collaboration analysis of diffractive structure function and diffractive dijets at HERA. We calculated cross-section for single and central diffractive production of dileptons. Cross-sections for exclusive and inclusive diffractive processes are compared.

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Open and hidden charm and beauty are of outstanding importance for the study of the strongly interacting Quark-Gluon Plasma (sQGP) discovered at RHIC, for example for the understanding of the mass dependence of jet quenching and the measure of the density of the partonic medium, and for the measurement of its temperature through the quarkonia dissociation hierarchy. We review selected highlights on charm and beauty production at RHIC from \(p+p\), \(d+\)Au and \(A+A\) collisions at \(\sqrt {s_{NN}}=200\) GeV, and compare them to model calculations. We focus on two particular issues, jet quenching and quarkonia.