scholarly journals Causality and Renormalization in Finite-Time-Path Out-of-Equilibrium ϕ3 QFT

Particles ◽  
2019 ◽  
Vol 2 (1) ◽  
pp. 92-102 ◽  
Author(s):  
Ivan Dadić ◽  
Dubravko Klabučar
Keyword(s):  
Finite Time ◽  
Matrix Theory ◽  
Heavy Ion ◽  
Potential Conflict ◽  
Composite Object ◽  
Self Energy ◽  
Time Path ◽  
Ion Collisions ◽  
S Matrix ◽  
Short Time

Our aim is to contribute to quantum field theory (QFT) formalisms useful for descriptions of short time phenomena, dominant especially in heavy ion collisions. We formulate out-of-equilibrium QFT within the finite-time-path formalism (FTP) and renormalization theory (RT). The potential conflict of FTP and RT is investigated in g ϕ 3 QFT, by using the retarded/advanced ( R / A ) basis of Green functions and dimensional renormalization (DR). For example, vertices immediately after (in time) divergent self-energy loops do not conserve energy, as integrals diverge. We “repair” them, while keeping d < 4 , to obtain energy conservation at those vertices. Already in the S-matrix theory, the renormalized, finite part of Feynman self-energy Σ F ( p 0 ) does not vanish when | p 0 | → ∞ and cannot be split to retarded and advanced parts. In the Glaser–Epstein approach, the causality is repaired in the composite object G F ( p 0 ) Σ F ( p 0 ) . In the FTP approach, after repairing the vertices, the corresponding composite objects are G R ( p 0 ) Σ R ( p 0 ) and Σ A ( p 0 ) G A ( p 0 ) . In the limit d → 4 , one obtains causal QFT. The tadpole contribution splits into diverging and finite parts. The diverging, constant component is eliminated by the renormalization condition ⟨ 0 | ϕ | 0 ⟩ = 0 of the S-matrix theory. The finite, oscillating energy-nonconserving tadpole contributions vanish in the limit t → ∞ .

scholarly journals Direct Photons from Hot Quark Matter in Renormalized Finite-Time-Path QED

Particles ◽  
2020 ◽  
Vol 3 (4) ◽  
pp. 676-692
Author(s):  
Ivan Dadić ◽  
Dubravko Klabučar ◽  
Domagoj Kuić
Keyword(s):  
Finite Time ◽  
Photon Emission ◽  
Heavy Ion ◽  
Uncertainty Relations ◽  
Quantum Field ◽  
Direct Photons ◽  
Basic Difference ◽  
Time Path ◽  
Ion Collisions ◽  
Hot Quark Matter

Within the finite-time-path out-of-equilibrium quantum field theory (QFT), we calculate direct photon emission from early stages of heavy ion collisions, from a narrow window, in which uncertainty relations are still important and they provide a new mechanism for production of photons. The basic difference with respect to earlier calculations, leading to diverging results, is that we use renormalized QED of quarks and photons. Our result is a finite contribution that is consistent with uncertainty relations.

scholarly journals Unified Theory of Electrons and Photons in Heavy Ion Collisions

1980 ◽  
Vol 35 (6) ◽  
pp. 579-589 ◽  
Author(s):  
Johannes Kirsch
Keyword(s):  
Electromagnetic Field ◽  
Heavy Ion Collisions ◽  
Matrix Theory ◽  
Heavy Ion ◽  
Unified Theory ◽  
Electron Systems ◽  
New Approach ◽  
Ion Collisions ◽  
S Matrix ◽  
Molecular Radiation

We present a unified formulation of the interaction of electrons with the electromagnetic field in heavy ion collisions, based on quantized interacting fields. This reduces the effort in treating many-electron systems substantially, as compared with the usual S-matrix theory. Both formalisms are shown to be equivalent. The simplification achieved by our new approach is demonstrated in detail for the example of quasi-molecular radiation

Interacting Hadron resonance gas model within S-matrix formalism

2019 ◽  
Vol 28 (09) ◽  
pp. 1940001 ◽  
Author(s):  
Ashutosh Dash ◽  
Subhasis Samanta
Keyword(s):  
Virial Coefficients ◽  
Heavy Ion ◽  
Phase Shifts ◽  
Matrix Formalism ◽  
Ion Collisions ◽  
S Matrix ◽  
Scattering Phase ◽  
Thermodynamic Variables ◽  
K Matrix ◽  
Dynamical Information

A noninteracting hadron resonance gas model is used often to study the hadronic phase formed in heavy ion collisions. Interaction among various hadronic constituents can be included using an S-matrix-based virial expansion approach. The virial coefficients require the dynamical information about the scattering phase shifts, which is used to compute various thermodynamic observables of an interacting hadronic gas. The attractive part of the phase shifts are calculated using K-matrix formalism while the repulsive part is obtained by fitting to experimental data. Calculation of various thermodynamic variables like pressure, energy density, specific heat capacity, etc., along with the second and higher-order correlations and fluctuations of conserved charges are done, first with only attraction and then with both attraction and repulsion included. Comparison of S-matrix results indicate a better agreement with lattice QCD data than the ideal HRG model across all thermodynamic variables.

scholarly journals Quarkonia disintegration due to time dependence of the qq̄ potential in relativistic heavy-ion collisions

2015 ◽  
Vol 30 (32) ◽  
pp. 1550162 ◽  
Author(s):  
Partha Bagchi ◽  
Ajit M. Srivastava
Keyword(s):  
Survival Probability ◽  
Heavy Ion Collisions ◽  
Hadron Collider ◽  
Heavy Ion ◽  
Gluon Plasma ◽  
Relativistic Heavy Ion Collisions ◽  
Relativistic Heavy Ion Collider ◽  
Ion Collisions ◽  
Quarkonium State ◽  
Short Time

Rapid thermalization in ultra-relativistic heavy-ion collisions leads to fast changing potential between a heavy quark and antiquark from zero temperature potential to the finite temperature one. Time-dependent perturbation theory can then be used to calculate the survival probability of the initial quarkonium state. In view of very short time scales of thermalization at relativistic heavy-ion collider (RHIC) and large hadron collider (LHC) energies, we calculate the survival probability of [Formula: see text] and [Formula: see text] using sudden approximation. Our results show that quarkonium decay may be significant even when temperature of quark–gluon plasma (QGP) remains low enough so that the conventional quarkonium melting due to Debye screening is ineffective.

scholarly journals K−/K+ratio in heavy-ion collisions with an antikaon self-energy in hot and dense matter

2003 ◽  
Vol 68 (2) ◽  
Author(s):  
Laura Tolós ◽  
Artur Polls ◽  
Angels Ramos ◽  
Jürgen Schaffner-Bielich
Keyword(s):  
Heavy Ion Collisions ◽  
Dense Matter ◽  
Heavy Ion ◽  
Self Energy ◽  
Ion Collisions

LIGHT CLUSTERS IN NUCLEAR MATTER

2010 ◽  
Vol 24 (25n26) ◽  
pp. 4993-5009
Author(s):  
GERD RÖPKE
Keyword(s):  
Surrounding Medium ◽  
Mean Field ◽  
Dense Matter ◽  
Heavy Ion ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Pauli Blocking ◽  
Self Energy ◽  
Ion Collisions ◽  
Protons And Neutrons

Nuclei in dense matter are influenced by the medium. In the cluster mean-field approximation, an effective Schrodinger equation for the A-nucleon cluster is obtained accounting for the effects of the surrounding medium, such as self-energy and Pauli blocking. Similar to the single-baryon states (free protons and neutrons), the light elements (A ≤ 4) are treated as quasiparticles. Fit formulae are given for the quasiparticle shifts as function of temperature, density, asymmetry, and momentum. Composition, quantum condensates and thermodynamic functions are considered. The relevance for nuclear structure, heavy ion collisions and supernova astrophysics is shown.

scholarly journals A dynamical quasiparticle approach for the QGP bulk and transport properties

2016 ◽  
Vol 25 (07) ◽  
pp. 1642003 ◽  
Author(s):  
Hamza Berrehrah ◽  
Elena Bratkovskaya ◽  
Thorsten Steinert ◽  
Wolfgang Cassing
Keyword(s):  
Cross Sections ◽  
Degrees Of Freedom ◽  
Chemical Potential ◽  
Good Description ◽  
Charm Quark ◽  
Heavy Ion ◽  
Entropy Density ◽  
Self Energy ◽  
Ion Collisions ◽  
Transport Studies

The properties of quantum chromodynamics (QCD) nowadays are accessible by lattice QCD calculations at vanishing quark chemical potential [Formula: see text], but often lack a transparent physical interpretation. In this review, we report about results from an extended dynamical quasiparticle model (DQPM[Formula: see text]) in which the effective parton propagators have a complex self-energy that depends on the temperature [Formula: see text] of the medium as well as on the chemical potential [Formula: see text] and the parton three-momentum [Formula: see text] with respect to the medium at rest. It is demonstrated that this approach allows for a good description of QCD thermodynamics with respect to the entropy density, pressure, etc. above the critical temperature [Formula: see text] 158 MeV. Furthermore, the quark susceptibility [Formula: see text] and the quark number density [Formula: see text] are found to be reproduced simultaneously at zero and finite quark chemical potential. The shear and bulk viscosities [Formula: see text], and the electric conductivity [Formula: see text] from the DQPM[Formula: see text] also turn out in close agreement with lattice results for [Formula: see text] =0. The DQPM[Formula: see text], furthermore, allows to evaluate the momentum [Formula: see text], [Formula: see text] and [Formula: see text] dependencies of the partonic degrees of freedom also for larger [Formula: see text] which are mandatory for transport studies of heavy-ion collisions in the regime 5[Formula: see text]GeV [Formula: see text] 10[Formula: see text]GeV. We finally calculate the charm quark diffusion coefficient [Formula: see text] – evaluated from the differential cross-sections of partons in the medium for light and heavy quarks by employing the propagators and couplings from the DQPM – and compare it to the available lattice data. It is argued that the complete set of observables allows for a transparent interpretation of the properties of hot QCD.

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