Falk Bruckmann
Instantons at finite temperature consist of dyons, with their masses depending on the asymptotic Polyakov loop. It is shown that the suppression of heavy dyons can explain qualitatively the behavior of the periodic and antiperiodic chiral condensate and the topological susceptibility above the phase transition.
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We study mesonic and baryonic correlation functions in the temporal directions in the vicinity of the critical temperature $T\simeq T_c$ using the instanton liquid model. In this model chiral symmetry restoration is driven by the formation of instanton-antiinstanton molecules. Although we find the signals for all hadronic poles to be drastically reduced, some hadronic states seem to survive the phase transition, as loosely bound $U(N_f)\times U(N_f)$ chiral multiplets in the plasma phase. These states are the $0^+ - 0^-$ mesons $(π,σ,η',δ)$ and the $N(\frac{1}{2}^+) - N(\frac{1}{2}^-)$ baryons…
In the holographic model of QCD, theta dependence sharply changes at the point of confinement deconfinement phase transition. In large N QCD such a change in theta behavior can be related to the breakdown of the instanton expansion at some critical temperature T_c. Associating this temperature with confinement-deconfinement phase transition leads to the description of the latter in terms of dissociation of instantons into the fractionally charged instanton quarks. To elucidate this picture, we introduce the nonvanishing chiral condensate in the deconfining phase and assume a specific lagrangia…
We present arguments suggesting that large size overlapping instantons are the driving mechanism of the confinement-deconfinement phase transition at nonzero chemical potential mu. The arguments are based on the picture that instantons at very large chemical potential in the weak coupling regime are localized configurations with finite size ρ\simμ^{-1}. At the same time, the same instantons at smaller chemical potential in the strong coupling regime are well represented by the so-called instanton-quarks with fractional topological charge 1/N_c. We estimate the critical chemical potential mu_c(…
We present an evaluation of the fluctuation determinant which appears as a prefactor in the instanton transition rate for the two-dimensional Abelian Higgs model. The corrections are found to change the rate at most by a factor of 2 for 0.4 < M_W/M_H < 2.0.
We explore the idea that the chiral phase transition in QCD can be described as a transition from a disordered instanton liquid to a strongly correlated phase of polarized instanton anti-instanton molecules. We find a number of non perturbative effects caused by the presence of instantons above T_c, among them the fact that instantons contribute to the euquation of state. We also study how instantons affect the propagation of light quarks at high temperature and determine the spacelike screening masses for mesons and baryons. We derive the corresponding effective interaction and find that the …
A simple model for the instanton ensemble at finite temperature T is proposed, including ``random" and strongly correlated ``molecular" component. T-dependence of fermionic zero modes naturally leads to chiral symmetry restoration, without instanton suppression. Moreover, at $T=(1-2) T_c$ the non-perturbative effects due to ``molecules" are so strong, that they even dominate the global thermodynamics. % two figures are enclosed as .ps files
We have reinvestigated the collision of gluonic bubbles in a SU(2) model of QCD which was studied by Johnson, Choi and Kisslinger in the context of the instanton-inspired model of QCD phase transition bubbles with plane wave approximation. We discuss treacherous points of the instanton-inspired model that cause the violation of causality due to the presence of imaginary gluon fields. By constructing a new slightly modified Lorentzian model where we have three independent real gluon fields, we reanalyzed the process of bubble collisions. Our numerical results show some indication of forming a b…
We study an interacting ensemble of instantons at finite baryon chemical potential. We emphasize the importance of fermionic zero modes and calculate the fermion induced interaction between instantons at non-zero chemical potential. We show that unquenched simulations of the instanton ensemble are feasible in two regimes, for sufficiently small and for very large chemical potential. At very large chemical potential chiral symmetry is restored and the instanton ensemble is dominated by strongly correlated chain-like configurations.
We investigate instantons in finite temperature QCD via Witten's holographic QCD. To study the deconfinement phase, we use the setup proposed in [1] (arXiv:1107.4048). We find that the sizes of the instantons are stabilized at certain values both in the confinement and deconfinement phases. This agrees with the numerical result in the lattice gauge theory. Besides we find that the gravity duals of the large and small instantons in the deconfinement phase have different topologies. We also argue that the fluctuation of the topological charges is large in confinement phase while it is exponentia…
We present arguments suggesting that large size overlapping instantons are the driving mechanism of the confinement-deconfinement phase transition at nonzero chemical potential mu. The arguments are based on the picture that instantons at very large chemical potential in the weak coupling regime are localized configurations with finite size rho~1/mu. At the same time, the same instantons at smaller chemical potential in the strong coupling regime are well represented by the so-called instanton-quarks with fractional topological charge 1/Nc. We estimate the critical chemical potential mu_c(T) w…
We present the first examples of cosmological solutions to four-dimensional heterotic models which include an evolving bundle modulus. The particular bundle modulus we consider corresponds to the width of a gauge five brane. As such our solutions can be used to describe the evolution in one of these models after a small instanton transition. We find that certain properties are generic to these solutions, regardless of initial conditions. This enables us to make some definite statements about the dynamics subsequent to a small instanton transition despite the fact that we cannot microscopically…
We study the dynamics of the first order phase transition in the two dimensional 15-state Potts model, both at and off equilibrium. We find that phase changes take place through nucleation in both cases, and finite volume effects are described well through an instanton computation. Thus a dynamical measurement of the surface tension is possible. We find that the order-disorder surface tension is compatible with perfect wetting. An accurate treatment of fluctuations about the instanton solution is seen to be of great importance.
In the instanton models the chiral phase transition is driven by a transition from random instanton-antiinstanton liquid and correlated instanton-antiinstanton molecules. So far this phenomenon was studied by numerical simulations, while we develop alternative semi-analytic approach. For two massless quark flavors, both instantons and ``molecules" generate specific 4-fermion effective interactions. After those are derived, we determine the temperature dependence of the thermodynamic quantities, the quark condensate and the fraction of molecules using standard mean field method. Using Bethe-Sal…
It is shown that periodic instanton solutions may have bifurcations which qualitatively change the behaviour of the finite temperature transition rate. These bifurcations are studied numerically in a quantum mechanical model and in the massive two-dimensional sigma model with the Skyrme term. General rules which determine the behaviour of periodic instantons near bifurcations are derived and applied to the Electroweak Theory.
Instanton-dyons, also known as instanton-monopoles or instanton-quarks, are topological constituents of the instantons at nonzero temperature and holonomy. We perform numerical simulations of the ensemble of interacting dyons for the SU(2) pure gauge theory. Unlike previous studies, we focus on back reaction on the holonomy and the issue of confinement. We calculate the free energy as a function of the holonomy and the dyon densities, using standard Metropolis Monte Carlo and integration over parameter methods. We observe that as the temperature decreases and the dyon density grows, its minimu…
In this paper we study the statistical mechanics of the instanton liquid in QCD. After introducing the partition function as well as the gauge field and quark induced interactions between instantons we describe a method to calculate the free energy of the instanton system. We use this method to determine the equilibrium density and the equation of state from numerical simulations of the instanton ensemble in QCD for various numbers of flavors. We find that there is a critical number of flavors above which chiral symmetry is restored in the groundstate. In the physical case of two light and one…
We examine the role of instantons in the zero-temperature chiral phase transition in an SU(N) gauge theory. For a range of N_f (the number of fermion flavors) depending on N, the theory exhibits an infrared fixed point at coupling $α_*$. As N_f decreases, $α_*$ increases, and it eventually exceeds a critical value sufficient to trigger chiral symmetry breaking. For the case N = 2, we estimate the critical values of N_f and $α_*$ due to instantons by numerically solving a gap equation with an instanton-generated kernel. We find instanton effects of strength comparable to that of gluon exchange.
Using the liquid instanton model continued into Minkowski space and modified for finite temperature, the energy momentum tensor and the surface tension for buble walls during the QCD phase transition are derived. The resulting surface tension is in agreement with lattice calculations. Application to bubble collisions is discussed.
Instanton-like transitions (``shadow processes'') are considered in (1+1) dimensional models with one scalar field whose potential is a quadratic well with a cliff. The corresponding classical boundary value problem is solved, and the semiclassical transition probabilities are found in a rather wide range of energies and the numbers of initial particles.
We discuss implications of open string theory in B-violating low energy physics. In particular, exotic instantons can dynamically generate effective six quarks' operator, leading to a neutron-antineutron transition. Proton is not destabilized and flavor changing neutral currents are under control.
We study the properties of an instanton ensemble in three-flavor dense QCD which can be regarded as an instanton plasma weakly interacting by exchanging the eta' mesons. Based on this description, we explore the chiral phase transition induced by the instanton ensemble at high baryon density in analogy with the Berezinskii-Kosterlitz-Thouless transition. Using the renormalization group approach, we show that the instanton ensemble always behaves as a screened and unpaired plasma. We also demonstrate that the chiral condensate in dense QCD is proportional to the instanton density.
We investigate the generalized $K\to π$ transition vector and tensor form factors, from which we derive the transverse quark spin density in the course of the $K\toπ$ transition, based on the nonlocal chiral quark model from the instanton vacuum. The results of the transition tensor form factor are in good agreement with recent data of lattice QCD. The behavior of the transverse quark spin density of the $K\toπ$ transition turn out to be very similar to those of the pion and the kaon.
We investigate the mass spectrum and electromagnetic transitions of charmonia, emphasizing the instanton effects on them. The heavy-quark potential consists of the Coulomb-like potential from one-gluon exchange and the linear confining potential. We introduce the nonperturbative heavy-quark potential derived from the instanton vacuum. We also consider the screened confining potential, which better describes the electromagnetic decays of higher excited states. Using this improved heavy-quark potential, we compute the mass spectrum and electromagnetic decays of the charmonia. Focusing on the ins…
The one-loop fermionic contribution to the probability of an instanton transition with fermion number violation is calculated in the chiral Abelian Higgs model in 1+1 dimensions, where the fermions have a Yukawa coupling to the scalar field. The dependence of the determinant on fermionic, scalar and vector mass is determined. We show in detail how to renormalize the fermionic determinant in partial wave analysis, which is convenient for computations.
Winding number transitions in the two dimensional softly broken O(3) nonlinear sigma model are studied at finite energy and temperature. New periodic instanton solutions which dominate the semiclassical transition amplitudes are found analytically at low energies, and numerically for all energies up to the sphaleron scale. The Euclidean period beta of these finite energy instantons increases with energy, contrary to the behavior found in the abelian Higgs model or simple one dimensional systems. This results in a sharp crossover from instanton dominated tunneling to sphaleron dominated thermal…
We compute the first order chiral phase transition for an instanton motivated quark model with a local six-quark interaction. In order to compare different solutions of the gap equation we compute the bosonic effective action -- a two particle irreducible free energy functional. We find that the first order transition ends for a critical current quark mass, with continuous crossover for larger quark masses. Furthermore, we investigate different possible order parameters, including a color octet condensate. We also compare our formalism with mean field theory.
In $N+1$ dimensions, false vacuum decay at zero temperature is dominated by the $O(N+1)$ symmetric instanton, a sphere of radius $R_0$, whereas at temperatures $T>>R_0^{-1}$, the decay is dominated by a `cylindrical' (static) $O(N)$ symmetric instanton. We study the transition between these two regimes in the thin wall approximation. Taking an $O(N)$ symmetric ansatz for the instantons, we show that for $N=2$ and $N=3$ new periodic solutions exist in a finite temperature range in the neighborhood of $T\sim R_0^{-1}$. However, these solutions have higher action than the spherical or the cylindr…
The non-perturbative quark-gluon interaction depends significantly on the value of the quark mass. In particular, in the light quark mass regime, correlations are strongly influenced by dynamics associated to chiral symmetry breaking. We use the Interacting Instanton Liquid Model (IILM) as a tool to investigate the microscopic dynamical mechanisms which underly the dependence on the quark mass and drive the transition into the chiral regime of QCD. To ensure the validity of the model, we first verify that the dependence on the quark mass for several observables calculated in the IILM agrees we…
We consider winding number transitions in the two dimensional O(3) non-linear sigma model, modified by a suitable conformal symmetry breaking term. We discuss the general properties of the relevant instanton solutions which dominate the transition amplitudes at finite energy, and find the solutions numerically. The Euclidean period of the solution increases with energy, contrary to the behavior found in the abelian Higgs model or simple one dimensional systems. This indicates that there is a sharp crossover from instanton dominated tunneling to sphaleron dominated thermal activation at a certa…
We consider the de Sitter cosmology deformed by the presence of a thermal bath of radiation and/or time-dependent moduli fields. Depending on the parameters, either a first or second order phase transition can occur. In the first case, an instanton allows a double analytic continuation. It induces a probability to enter the inflationary evolution by tunnel effect from another cosmological solution. The latter starts with a big bang and, in the case the transition does not occur, ends with a big crunch. A temperature duality exchanges the two cosmological branches. In the limit where the pure d…
We study cold nuclear matter based on the holographic gauge theory, where baryons are introduced as the instantons in the probe D8/D8 branes according to the Sakai-Sugimoto model. Within a dilute gas approximation of instantons, we search for the stable states via the variational method and fix the instanton size. We find the first order phase transition from the vacuum to the nuclear matter phase as we increase the chemical potential. At the critical chemical potential, we could see a jump in the baryon density from zero to a finite definite value. While the size of the baryon in the nuclear …
Paradigme shift in gauge topology, from instantons to their constituents -- instanton-dyons -- has recently lead to very significant advances. Like instantons, they have fermionic zero modes, and their collectivization at sufficiently high density explains the chiral symmetry breaking. Unlike instantons, these objects have electric and magnetic charges. Their back reaction on the mean value of the Polyakov line (holonomy) allows to explain the deconfinement transition. The talk summarizes recent works on the dyon ensemble, done in the mean field approximation (MFA), and also by direct numerica…
Two-parameter sets of solutions to the classical field equations in the massless $ϕ^4$ model and SU(2) gauge theory are found, each solution presumably describing a multi-particle instanton-like transition at high energy. In the limit of small number of initial particles, the probability of the transition is suppressed by $\exp(-2S_0)$, where $S_0$ is the instanton action.
Studying the instanton-induced contributions to various hard exclusive reactions provides physical insight into the transition from the non-perturbative to the perturbative regime of QCD. To this end, we study the leading-instanton contribution to the electro-magnetic and transition formfactors, using an effective theory of the Instanton Liquid Model. We report predictions for the space-like electro-magnetic formfactor of the pion, as well as recent results for the Dirac formfactor of the proton.
A solution to the classical field equations in the massless (1+1)-dimensional O(3) sigma model is found, which describes a multi-particle instanton-like transition at high energy. In the limit of small number of initial particles, the number of final particles is shown to be also small, and the probability of the transition is suppressed by $\exp(-2S_0)$, where $S_0$ is the instanton action. This solution, however, does not correspond to the maximum transition probability among all states with given number of incoming particles and energy. Unless the limit $g^2 n_{initial}\to0$ is exponentiall…
In quantum chromodynamics (QCD), the role which topologically non-trivial configurations play in splitting the singlet pseudo-Goldstone meson, the $η^\prime$, from the octet is familiar. In addition, such configurations contribute to other processes which violate the axial $U(1)_A$ symmetry. While the nature of topological fluctuations in the confined phase is still unsettled, at temperatures well above that for the chiral phase transition, they can be described by a dilute gas of instantons. We show that instantons of arbitrary topological charge $Q$ generate anomalous interactions between $2…
We consider classical Minkowskian solutions to the field equation in the (1+1) dimensional scalar model with the exponential interaction that describe the unsuppressed false vacuum decay induced by $n$ initial particles. We find that there is a critical value of $n$ below which there are no such solutions, i.e., the vacuum decay is always suppressed. For the number of initial particles larger than this value the vacuum decay is unsuppressed at high enough energies.
In companion papers \cite{Addazi:2015pia,Addazi:2016rgo}, we have discussed current bounds of a new super-light baryo-photon, associated to a $U(1)_{B-L}$ gauged, from neutron-antineutron current data, which are competitive with Eötvös type experiments. Here, we discuss the implications of a possible baryo-photon detection in string theory and quantum gravity. The discovery of a very light gauge boson should imply the violation of the Weak Gravity Conjecture, carrying deep consequences in our understanding of holography, quantum gravity and black holes. On the other hand, we show how the detec…
Confinement remains one the most interesting and challenging nonperturbative phenomenon in non-Abelian gauge theories. Recent semiclassical (for SU(2)) and lattice (for QCD) studies have suggested that confinement arises from interactions of statistical ensembles of instanton-dyons with the Polyakov loop. In this work, we extend studies of semiclassical ensemble of dyons to the $SU(3)$ Yang-Mills theory. We find that such interactions do generate the expected first-order deconfinement phase transition. The properties of the ensemble, including correlations and topological susceptibility, are s…
This is the last in a series of papers on the topological susceptibility in the interacting instanton liquid model (IILM). We will derive improved finite temperature interactions to study the thermodynamic limit of grand canonical Monte Carlo simulations in the quenched and unquenched case with light, physical quark masses. In particular, we will be interested in chiral symmetry breaking. The paper culminates by giving, for the first time, a well-motivated temperature-dependent axion mass. Especially, this work finally provides a computation of the axion mass in the low temperature regime, $m^…
We have shown an example of semiclassical transition in $ϕ^{4}$ theory with positive coupling constant. This process can be described by the classical $O(4)$-invariant solution, considered on a contour in the complex time plane. The transition is technically analogous to the one-instanton transition in the electroweak model. It is suppressed by the factor $\exp(-2S_{0})$, where $S_{0}$ is Lipatov instanton action. This process describes a semiclassical transition between two coherent states with much smaller number of particles in the initial state than in the final state. Therefore, it could …
The chiral phase transition of QCD is analyzed in a model combining random matrix elements of the Dirac operator with specially chosen non-random ones. The special form of the latter is motivated by the assumption that the fermionic quasi-zero modes associated with instanton and anti-instanton configurations determine the chiral properties of QCD. Our results show that the degree of correlation between these modes plays the decisive role. To reduce the value of the chiral condensate by more than a factor of 2 about 95 percent of the instantons and anti-instantons must form so-called molecules.…
We have shown an example of semiclassical transition in ϕ^4 model with positive coupling constant. This process describes a semiclassical transition between two coherent states with much smaller average number of particles in the initial state than in the final state. This transition is technically analogous to the one-instanton transition in the electroweak model. It is suppressed by the factor exp(-2S), where S is Lipatov instanton action. It could be important to the problem of calculation of amplitudes for multiparticle production in ϕ^4-type models.
We discuss nuclear matter and the transition to quark matter in the decompactified limit of the Sakai-Sugimoto model. Nuclear matter is included through instantons on the flavor branes of the model. Our approximation is based on the flat-space solution, but we allow for a dynamical instanton width and deformation and compute the energetically preferred number of instanton layers in the bulk as a function of the baryon chemical potential. We determine the regions in parameter space where the binding energy of nuclear matter is like in QCD, and compute the phase diagram in the plane of temperatu…
We study the connection between monopoles and instantons in the Polyakov-like gauge, and the behavior of the monopole trajectories generated by instantons at finite temperature. The monopole trajectories become long and complicated at the zero-temperature which can be regarded as monopole condensation. On the other hand, they tend to become simple at finite temperature. It is suggested that such a change is related to the confinement-deconfinement phase transition.
We study hadronic correlation functions in the interacting instanton liquid model, both at zero and nonzero temperature $T$. At zero $T$ we investigate the dependence of the correlators on the instanton ensemble, in particular the effect of the fermionic determinant. We demonstrate that quark-induced correlations between instantons are important, especially in the repulsive $η'$ and $δ$-meson channels. We also calculate a large number of mesonic and baryonic correlation functions as a function of temperature. We find three different types of behavior as $T\to T_c$. The vector channels $ρ,a_1,Δ…
In the large N limit cold dense nuclear matter must be in a lattice phase. This applies also to holographic models of hadron physics. In a class of such models, like the generalized Sakai-Sugimoto model, baryons take the form of instantons of the effective flavor gauge theory that resides on probe flavor branes. In this paper we study the phase structure of baryonic crystals by analyzing discrete periodic configurations of such instantons. We find that instanton configurations exhibit a series of "popcorn" transitions upon increasing the density. Through these transitions normal (3D) lattices …
In this work we present the results from numerical simulations of an interacting ensemble of instanton-dyons in the $SU(3)$ gauge group with $N_f=2$ flavors of massless quarks. Dynamical quarks are included via the effective interactions induced by the fermionic determinant evaluated in the subspace of topological zero modes. The eigenvalue spectrum of the Dirac operator is studied at different volumes to extract the chiral condensate and eigenvalue gap, with both observables providing consistent values of the chiral transition temperature $T_c$. We find that a sufficient density of dyons is r…
We discuss an alternative for Baryon-violating six quarks transitions, in the contest of low scale string theory. In particular, with $M_{S}=10÷10^{3}\rm TeV$, such a transition can be mediated by two color-triplets,through a quartic coupling with down-quarks,generated by exotic instantons, in a calculable and controllable way. We show how FCNCs limits on color-triplet massare well compatible with $n-\bar{n}$ oscillation ones. If a $n-\bar{n}$ transition were found, this would be an indirect hint for our model. This would strongly motivate researches of direct channels in proton-proton collide…
"Exotic quarks" in the title refers to a modification of quark periodicity condition on the thermal circle by introduction of some phases -- known also as "flavor holonomies" -- different quark flavors. These phases provide a valuable tool, to be used for better understanding of deconfinement and chiral restoration phase transitions: by changing them one can dramatically modify both phase transitions. In the language of instanton constituents -- instanton-dyons or monopoles -- it has a very direct explanation: the interplay of flavor and color holonomies can switch topological zero modes betwe…
Ground state and radial excitation mass spectra of bottomonium states are computed using the Instanton Induced $q \bar{q}$ Potential obtained from Instanton Liquid Model for QCD vacuum. The Schrodinger equation is solved for two body problem using variational method. Hyperfine interactions are incorporated to remove the degeneracy between spin singlet and spin triplet states of $S$ wave masses. Spin-orbit and tensor interactions through one gluon exchange has been added to the spin average masses of P and D wave states. The vector decay constants and pseudoscalar decay constants are also estim…
Instantons create a non-local interaction between the quarks, which at finite baryon density leads to the formation of a scalar diquark condensate and color superconductivity. A mean field approach leads to a self-consistent description of the $<\bar q q>$ and $<q q>$ condensates and shows the inevitability of a BCS type instability at the Fermi surface. The role of the rearrangement of the instanton ensemble for the QCD phase transitions is also discussed.
We discuss recently formulated instanton-torus knot duality in $Ω$-deformed 5D SQED on $\mathbb{R}^4 \times S^1$ focusing at the microscopic aspects of the condensate formation in the instanton ensemble. Using the chain of dualities and geometric transitions we embed the SQED with a surface defect into the $SU(2)$ SQCD with $N_f=4$ and identify the numbers $(n,m)$ of the torus $T_{n,m}$ knot as instanton charge and electric charge. The HOMFLY torus knot invariants in the fundamental representation provide entropic factor in the condensate of the massless flavor counting the degeneracy of the i…
The electroweak phase transition in a constant hypermagnetic field=A0 is studied in the Standard Model. The symmetry behaviour is investigated within the consistent effective potential of the scalar and magnetic fields at finite temperature. It includes the one-loop and ring diagram contributions. All fundamental fermions and bosons are taken into consideration with their actual masses. The only free parameter is the Higgs boson mass which is chosen to be in the energy interval 75 GeV $\le m_H \le$=A0 115 GeV.=A0 It is found that for the field strengths $H \sim 10^{22}- 10^{23}$G the electrowe…
Pion transition form factor for the process $γ*γ*\to π^0$ at space-like values of photon momenta is calculated within the effective quark-meson model with the interaction induced by instanton exchange. The leading and next-to-leading order power asymptotics of the form factor and the relation between the light-cone pion distribution amplitudes of twists 2 and 4 and the dynamically generated quark mass are found.
Both in heavy-ion collisions as in magnetars very strong magnetic fields are produced, which has its influence on the phases of matter involved. In this paper we investigate the effect of strong magnetic fields (B = 5 m_pi^2 /e = 1.7 x 10^19 G) on the chiral symmetry restoring phase transition using the Nambu-Jona-Lasinio model. It is observed that the pattern of phase transitions depends on the relative magnitude of the magnetic field and the instanton interaction strength. We study two specific regimes in the phase diagram, high chemical potential and zero temperature and vice versa, which a…
The properties of the QCD partition function at finite chemical potential are studied within the instanton liquid model. It is shown that the density dependence of the quark-induced instanton-antiinstanton (I-A) interaction leads to the formation of topologically neutral I-A pairs ('molecules'), resulting in a first order chiral phase transition at a critical chemical potential $μ_q^c\simeq 310$ MeV. At somewhat higher densities ($μ_q\ge360$ MeV), the quark Fermi surface becomes instable with respect to diquark condensation (Cooper pairs) generating BCS-type energy gaps of order 50 MeV.
We investigate the phase transitions characterized by deconfinement and restoration of chiral and axial symmetries,at finite temperature, in the framework of QCD inspired models. We compare the results obtained in the SU(2) Polyakov-Nambu-Jona-Lasinio model with anomaly and in its extended version, the Entangled Polyakov-Nambu-Jona-Lasinio model. In the last version, four-quark vertices with entanglement between the chiral condensate and the Polyakov loop are considered. The thermodynamics of the phase transitions, the meson spectrum, and in particular the convergence of axial and chiral partn…
We study the confinement phase transition in $SU(2)$ Yang-Mills theory, based on a statistical ensemble model of correlated instanton-dyons. We show for the first time that such a model provides a quantitative description, in light of the lattice data, for the temperature dependence of the order parameter. We characterize the short-range interaction which plays a crucial role for the properties of such ensemble. The chromo-magnetic charge density as well as the spatial correlations is found to be consistent with known lattice and phenomenological information.
This talk consists of two very different parts: the first one deals with non-perturbative QCD and physics of the chiral restoration, the second with rather low-key (and still unfinished) work aiming at obtaining EOS and other properties of hot/dense hadronic matter from data on heavy ion collisions. The microscopic mechanism for chiral restoration phase transition is a transition from randomly placed tunneling events (instantons) at low T to a set of strongly correlated tunneling-anti-tunneling events (known as instanton - anti-instanton molecules) at high T. Many features of the transition ca…
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