Stochastic Vacuum Research Articles

Evolution of Colour in QCD and Informational Approach to Quantum Measurement

Quantum chromodynamics (QCD) introduces the quantum characteristic of colour in order to satisfy the Pauli exclusion principle and symmetric considerations for wavefunctions of hadrons. However, the particles that possess colour charge (quarks and gluons) are not directly observed in experiment – the effect which is often referred to as confinement. Confinement of quarks and gluons represents a theoretical challenge, as the dynamics of underlying fields is non-perturbative and therefore is problematic to be described analytically. One possible way is to use non-perturbative approaches and derive analogies with other well-established branches of physics. In this work we describe the use of the method of vacuum correlators – to analyze the confinement and other non-perturbative dynamics of quarks. The discussion of the acquired results is then given on the basis of quantum information and measurement description. It is shown that the confinement of quarks might be associated with the decoherence of colour state due to the interaction of colour charges with the environment of colour fields (QCD stochastic vacuum).

Searching for the Odderon in the diffractive f_2(1270) photoproduction at pA collisions

Although the Odderon is an unambiguous prediction of Quantum Chromodynamics, its existence still was not confirmed experimentally. One of the processes where the Odderon contribution is expected to be dominant is the diffractive photoproduction of tensor mesons. In this paper we study the diffractive f_2(1270) photoproduction in pA collisions at LHC and RHIC considering the model of the stochastic vacuum to treat the non-perturbative process. We demonstrate that this process dominates the f_2 production at mid-rapidities, and large values for the cross section are predicted. Our results indicate that the experimental analysis of this final state is, in principle, feasible and can be used to probe the Odderon.

Interaction of quantum systems with environment in QCD

It is shown that the interaction of quark with the stochastic vacuum of QCD (considered as an environment) leads to the decoherence of quark colour state, associated with the loss of information on the initial quark colour. We propose to consider this process as a reason of the confinement of the quark colour. Asymptotically this leads to confined quarks (fully mixed colourless quark states) in the limit of large distances and time intervals (confinement region) and free coloured quarks in the limit of small distances and time intervals (asymptotic freedom). We propose quantitative characteristics that allow to describe the process of interaction: purity, fidelity, von Neumann entropy, quantum information measure. The cases of two and arbitrary number of quarks are considered, and it is shown that the entanglement in such system disappears in the limit of large distances and time intervals. The process is in good agreement with the known theorems in quantum information theory (no-cloning and no-hiding). We study non-perturbative evolution of the gluon colour states during short time. Fluctuations of gluons are less than those for coherent states. This fact suggests that there gluon squeezed states can arise. Theoretical justification for the occurrence both singe- and two-mode gluon squeezing effects in QCD is given. We show that gluon entangled states which are closely related with two-mode squeezed states of gluon fields can appear at short time non-perturbative evolution by analogy with corresponding photon states in quantum optics.

Color screening in flux tubes and in the color Coulomb potential from QCD field correlators

Colorelectric and Colormagnetic structure of the flux tubes, connecting heavy quark and antiquark, is investigated in the framework of the Field Correlator method which describes all resulting fields in terms of correlators $D^E$ and $D^E_1$. The latter have been computed via gluelumps, which allows to predict the resulting distribution of color fields $\mathbf{E} (\mathbf{r}),$ and colormagnetic currents $\mathbf{k} (\mathbf{r})$ in the flux tubes. It is shown, that at large distances $r\gg \lambda \approx 0.2$ fm the whole structure of fields and relations between them is similar to that of the dual superconductor theory, but the basic dynamics, including small distances, is given by field correlators of the real stochastic vacuum. The important contradiction between the strong screening of color fields in the width of flux tubes and almost no screening in the perturbative $Q\bar Q$ potential is resolved.

Decoherence of quantum states in QCD vacuum

The stochastic vacuum of quantum chromodynamics is used as an environment for quarks considered as color state vectors. It is shown that during interaction with the stochastic vacuum information of the quark color state is lost with time (decoherence of the quark state vector occurs), which effectively means that it is impossible to observe the quark as a free color particle (confinement).

Quantum Optics Properties of QCD Vacuum

Theoretical justification of the occurrence of multimode squeezed and entangled colour states in QCD is given. We show that gluon entangled states which are closely related with corresponding squeezed states can appear by the four-gluon self-interaction. Correlations for the collinear gluons are revealed two groups of the colour correlations which is significant at consider of the quark-antiquark pair productions.It is shown that the interaction of colour quark with the stochastic vacuum of QCD leads to the loss of information on the initial colour state of the particle, which gives a new perspective regarding the confinement of quarks phenomenon. The effect is demonstrated for a single particle and in the multiparticle case is proposed.Quantum characteristics (purity and von Neumann entropy) are used to analyse the process of interaction.

Stochastic vacuum of quantum chromodynamics as an environment for color particles

The behavior of quarks is described within approaches used in quantum mechanics and related disciplines (quantum optics and quantum theory of information). The stochastic vacuum of quantum chromodynamics is treated as an environment (closed pool) for color particles (quarks). Their interaction results in a loss of information on the quark color state and consequently in the impossibility of observing it (the confinement of quarks). The processes are described using quantities of the quantum theory of information, such as von Neumann entropy, fidelity, and purity.

Comparative study between Glauber-Velasco and the Stochastic Vacuum models for high energy hadronic collision

The outlines of the Glauber-Velasco (GV) and the Stochastic Vacuum models (SVM) for describing pp elastic scattering are presented. The amplitudes and the cross-sections of both models are investigated and compared at √s = 7TeV. The asymptotic energy behaviour for the SVM is also studied.

Colour Information Loss due to Decoherence in Vacuum

The model of stochastic vacuum of quantum chromodynamics might be used for an alternative treatment of subhadronic processes. The possibility of considering the stochastic vacuum as an environment for colour charges is discussed. It is shown that the interaction of colour particles with the stochastic vacuum leads to the decoherence process and the loss of information on the initial quantum state of the particle, which gives a new perspective regarding the confinement of quarks phenomenon.The mentioned effect is demonstrated in cases of a single particle and a superposition of colour charges. Generalization on the multiparticle case is proposed.Quantum characteristics (purity and von Neumann entropy) are used to analyse the process of interaction. On the base of von Neumann entropy the measure of quantum information is proposed.

Colour particle states behaviour in the QCD vacuum

The results of an interaction of a quantum state of quark with QCD vacuum, where the latter plays a role of environment, could be treated as decoherence. This may have direct implications for the confinement of quarks phenomenon.The general description and discussion of this process is given. Characteristics from quantum optics and information theory (purity, fidelity, von Neumann entropy) are proposed as means for numerical analysis of the process of interaction of quark colour state with stochastic vacuum.Problems of stability of colour particles motion and order-chaos transitions are briefly discussed. It is shown that there should be a connection between the properties of QCD stochastic vacuum and Higgs boson mass and self interaction coupling constant.The behaviour of squeezed and entangled quantum states, the interaction of colour superpositions and multiparticle states with stochastic QCD vacuum is described. It is shown that it leads to a fully mixed quantum state with equal probabilities for different colours. Decoherence rate is found to be proportional to the product of the distance between colour charges and the time during which this interaction has taken place. I.e. such an interaction seems to lead naturally to confinement of quarks.

Confinement of color states in a stochastic vacuum of quantum chromodynamics

We show that in the framework of the stochastic vacuum model of quantum chromodynamics, quark confinement can be described as the decoherence of a color state of a particle into a mixed quantum state with equal probabilities for different colors. We evaluate the quantum characteristics of one-particle and multiparticle states: purity, fidelity, and the von Neumann entropy.

Quantum liquids resulting from quark systems with four-quark interaction

Quark ensembles influenced by strong stochastic vacuum gluon fields are investigated within the four-fermion interaction approximation. The comparative analysis of several quantum liquid models is performed and this analysis leads to the conclusion that the presence of a gas–liquid phase transition is their characteristic feature. The problem of the instability of small quark number droplets is discussed and it is argued that it is rooted in the chiral soliton formation. The existence of a mixed phase of the vacuum and baryon matter is proposed as a possible explanation of the latter stability.

On the Casimir operator dependences of QCD amplitudes

In eikonal and quenched approximations at least, it is argued that the strong-coupling fermionic QCD amplitudes based on the newly discovered effective locality property, depart from a dependence on the sole quadratic Casimir operator, evaluated over the fundamental gauge group representation: A definite dependence on the cubic SU(3) Casimir operator takes place. This result, in contradistinction to perturbation theory, but also to a number of non-perturbative approaches such as the MIT bag, the stochastic vacuum models, and lattice simulations, accounts, instead, for the full algebraic content of the rank-2 Lie algebra.

Quark condensate for various heavy flavors

The quark condensate is calculated within the world-line effective-action formalism, by using for the Wilson loop an ansatz provided by the stochastic vacuum model. Starting with the relation between the quark and the gluon condensates in the heavy-quark limit, we diminish the current quark mass down to the value of the inverse vacuum correlation length, finding in this way a 64%-decrease in the absolute value of the quark condensate. In particular, we find that the conventional formula for the heavy-quark condensate cannot be applied to the c-quark, and that the corrections to this formula can reach 23% even in the case of the b-quark. We also demonstrate that, for an exponential parametrization of the two-point correlation function of gluonic field strengths, the quark condensate does not depend on the non-confining non-perturbative interactions of the stochastic background Yang-Mills fields.

Instanton screening in the nonperturbative QCD

The gluon field screening in the stochastic vacuum of gluodynamics is studied. The effective action is derived for the instanton interacting with nonperturbative fields. Quantum nonperturbative effects are shown to affect greatly the shape of instanton. The power asymptotics x−2 of the classical “instanton’s profile function” at large distances is replaced due to these effects by Airy function asymptotics.

Stochastic Models of Electromagnetic Vacuum in Resonance Phenomena

In this article, we both presented the concept of coherent and squeezed stochastic vacuum and simultaneously specified the way to calculate resonant fluorescent spectrum in two- or three-level system with configuration Λ in the presence of squeezed stochastic vacuum. The effects that occurred in the presence of squeezed stochastic vacuum were the change of both the width and the height of central spectrum and of additional narrow peaks. The impacts of squeezed vacuum on fluorescence spectrum represent the dependence on the squeezed parameter of both amplitude and phase. In the absence of unsqueezed vacuum, fluorescent spectrum returns to normal Mollow spectral type.

Quantum Mechanics as an Emergent Property of Ergodic Systems Embedded in the Zero-point Radiation Field

The present paper reveals (non-relativistic) quantum mechanics as an emergent property of otherwise classical ergodic systems embedded in a stochastic vacuum or zero-point radiation field (zpf). This result provides a theoretical basis for understanding recent numerical experiments in which a statistical analysis of an atomic electron interacting with the zpf furnishes the quantum distribution for the ground state of the H atom. The action of the zpf on matter is essential within the present approach, but it is the ergodic demand what ultimately leads to the matrix formulation of quantum mechanics. The paper thus represents a step forward in the quest for an elucidation of the fundamentals of quantum mechanics.

Worldline casting of the stochastic vacuum model and nonperturbative properties of QCD: General formalism and applications

The stochastic vacuum model for QCD, proposed by Dosch and Simonov, is fused with a worldline casting of the underlying theory, i.e. QCD. Important nonperturbative features of the model are studied. In particular, contributions associated with the spin-field interaction are calculated, and the validity of both the loop equations and of the Bianchi identity is explicitly demonstrated. As an application, a simulated meson-meson scattering problem is studied in the Regge kinematical regime. The process is modeled in terms of the helicoidal Wilson contour along the lines introduced by Janik and Peschanski in a related study based on an AdS/CFT-type approach. Working strictly in the framework of the stochastic vacuum model and in a semiclassical approximation scheme, the Regge behavior for the scattering amplitude is demonstrated. Going beyond this approximation, the contribution resulting from boundary fluctuations of the Wilson loop contour is also estimated.

Jet quenching parameter $\hat{q}$ in the stochastic QCD vacuum with Landau damping

We argue that the radiative energy loss of a parton traversing the quark-gluon plasma is determined by Landau damping of soft modes in the plasma. Using this idea, we calculate the jet quenching parameter of a gluon. The calculation is done in SU(3) quenched QCD within the stochastic vacuum model. At the LHC-relevant temperatures, the result depends on the gluon condensate, the vacuum correlation length, and the gluon Debye mass. Numerically, when the temperature varies from T=T_c to T=900 MeV, the jet quenching parameter rises from \hat q=0 to approximately 1.8 GeV^2/fm. We compare our results with the predictions of perturbative QCD and other calculations.

10.1007/s11450-008-1018-7

In the deconfinement phase of QCD quarks and gluons interact with the dense stochastic colour-magnetic vacuum. We consider the dynamics of quarks in this deconfinement phase using the Field Correlators Method and derive an effective nonperturbative inter-quark potential, in addition to the usual perturbative short-ranged interaction. We find the resulting angular-momentum-dependent interaction to be attractive enough to maintain bound states and, for light quarks (and gluons), to cause emission of quark and gluon pairs. Possible consequences for the strong interacting quark--gluon plasma are briefly discussed.