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A. N. Ivanov

Publications and source records attributed to A. N. Ivanov.

At least 109 records · Page 6Linked to original sources
arXiv2003

Bosonic vacuum wave functions from the BCS-type wave function of the ground state of the massless Thirring model

A BCS-type wave function describes the ground state of the massless Thirring model in the chirally broken phase. The massless Thirring model with fermion fields quantized in the chirally broken phase bosonizes to the quantum field theory of the free massless (pseudo)scalar field (Eur. Phys. J. C20, 723 (2001)). The wave functions of the ground state of the free massless (pseudo)scalar field are obtained from the BCS-type wave function by averaging over quantum fluctuations of the Thirring fermion fields. We show that these wave functions are orthogonal, normalized and non-invariant under shifts of the massless (pseudo)scalar field. This testifies the spontaneous breaking of the field-shift symmetry in the quantum field theory of a free massless (pseudo)scalar field. We show that the vacuum-to-vacuum transition amplitude calculated for the bosonized BCS-type wave functions coincides with the generating functional of Green functions defined only by the contribution of vibrational modes (Eur. Phys. J. C 24, 653 (2002)) . This confirms the assumption that the bosonized BCS-type wave function is defined by the collective zero-mode (hep-th/0212226). We argue that the obtained result is not a counterexample to the Mermin-Wagner-Hohenberg and Coleman theorems.

hep-th↗
arXiv2002

Quantum field theory of a free massless (pseudo)scalar field in 1+1-dimensional space-time as a test for the massless Thirring model

We analyse different approaches to the description of the quantum field theory of a free massless (pseudo)scalar field defined in 1+1-dimensional space-time which describes the bosonized version of the massless Thirring model. These are (i) axiomatic quantum field theory, (ii) current algebra and (iii) path-integral. We show that the quantum field theory of a free massless (pseudo)scalar field defined on the class of Schwartz's test functions S_0(R^2) connects all these approaches. This quantum field theory is well-defined within the framework of Wightman's axioms and Wightman's positive definiteness condition. The physical meaning of the definition of Wightman's observables on the class of test functions from S_0(R^2) instead of S(R^2), as required by Wightman's axioms, is the irrelevance of the collective zero-mode related to the collective motion of the ``center of mass'' of the free massless (pseudo)scalar field, which can be deleted from the intermediate states of correlation functions (Eur. Phys. J. C 24, 653 (2002)). In such a theory the continuous symmetry, induced by shifts of the massless (pseudo)scalar field, is spontaneously broken and there is a non-vanishing spontaneous magnetization. The obtained results are discussed in connection with Coleman's theorem asserting the absence of Goldstone bosons and spontaneously broken continuous symmetry in quantum field theories defined in 1+1-dimensional space-time.

hep-th↗
arXiv2002

Massless Thirring fermion fields in the boson field representation

We show that the boson field representation of the massless fermion fields, suggested by Morchio, Pierotti and Strocchi in J. Math. Phys. 33, 777 (1992) for the operator solution of the massless Thirring model, agrees completely with the existence of the chirally broken phase in the massless Thirring model revealed in EPJC 20, 723 (2001) and hep-th/0112183, when the free massless boson fields are described by the quantum field theory, free of infrared divergences in 1+1-dimensional space-time, formulated in hep-th/0112184 and hep-th/0204237.

hep-th↗
arXiv2002

On free massless (pseudo)scalar quantum field theory in 1+1-dimensional space-time

We construct a consistent quantum field theory of a free massless (pseudo)scalar field in 1+1-dimensional space-times free of infrared divergences. We show that a continuous symmetry of (pseudo)scalar field translations is spontaneously broken. Goldstone bosons appear as quanta of a free massless (pseudo)scalar field. We show that the main inequality between vacuum expectation values of certain operators which has been used for the derivation of the Mermin-Wagner-Hohenberg theorem is fulfilled in the quantum field theory of a free massless (pseudo)scalar field free of infrared divergences.

hep-th↗
arXiv2002

On the equivalence between sine-Gordon model and Thirring model in the chirally broken phase of the Thirring model

We investigate the equivalence between Thirring model and sine-Gordon model in the chirally broken phase of the Thirring model. This is unlike all other available approaches where the fermion fields of the Thirring model were quantized in the chiral symmetric phase. In the path integral approach we show that the bosonized version of the massless Thirring model is described by a quantum field theory of a massless scalar field and exactly solvable, and the massive Thirring model bosonizes to the sine-Gordon model with a new relation between coupling constants. We show that the non-perturbative vacuum of the chirally broken phase in the massless Thirring model can be described in complete analogy with the BCS ground state of superconductivity. The Mermin-Wagner theorem and Coleman's statement concerning the absence of Goldstone bosons in the 1+1-dimensional quantum field theories are discussed. We investigate the current algebra in the massless Thirring model and give a new value of the Schwinger term. We show that the topological current in the sine-Gordon model coincides with the Noether current responsible for the conservation of the fermion number in the Thirring model. This allows to identify the topological charge in the sine-Gordon model with the fermion number.

hep-th↗
arXiv2002

On the Solar Neutrino Problems, SNO experimental data and low-energy nuclear forces

The Solar Neutrino Problems (SNP's) are analysed within the Standard Solar Model (BP2000) supplemented by the reduction of the solar neutrino fluxes through the decrease of the solar core temperature. The former can be realized through the enhancement of the astrophysical factor for solar proton burning. The enhancement, the upper bound of which is restricted by the helioseismological data, goes dynamically due to low-energy nuclear forces described at the quantum field theoretic level. The agreement of the reduced solar neutrino fluxes with the experimental data is obtained within the scenario of vacuum two-flavour neutrino oscillations. We show that by fitting the mean value of the solar neutrino flux measured by HOMESTAKE Collaboration we predict the high energy solar neutrino flux measured by SNO Collaboration Phi(SNO(Boron))_th = 1.84 X 10^6 cm^(-2) s^(-1) in good agreement with the experimental value Phi(SNO(Boron))_exp = 1.75(0.14) X 10^6 cm^(-2) s^(-1) obtained via the measurement of the rate of reaction nu_e + D -> p + p + electron produced by boron solar neutrinos. The theoretical flux for low-energy neutrino flux measured by GALLIUM (GALLEX, GNO and SAGE) Collaborations S(Ga)_th = 65 SNU agrees with the experimental data averaged over experiments S(Ga)_exp = 75.6(4.8) SNU.

astro-ph↗
arXiv2001

On the solution of the massless Thirring model with fermion fields quantized in the chiral symmetric phase

Correlation functions of fermionic fields described by the massless Thirring model are analysed within the operator formalism developed by Klaiber and the path-integral approach with massless fermions quantized in the chiral symmetric phase. We notice that Klaiber's composite fermion operators possess non-standard properties under parity transformations and construct operators with standard parity properties. We find that Klaiber's parameterization of a one-parameter family of solutions of the massless Thirring model is not well defined, since it is not consistent with the requirement of chiral symmetry. We show that the dynamical dimensions of correlation functions depend on an arbitrary parameter induced by ambiguities of the evaluation of the chiral Jacobian. A non-perturbative renormalization of the massless Thirring model is discussed. We demonstrate that the infrared divergences of Klaiber's correlation functions can be transferred into ultra-violet divergences by renormalization of the wave function of fermionic fields. This makes Klaiber's correlation functions non-singular in the infrared limit. We show that the requirement of non-perturbative renormalizability of the massless Thirring model fixes a free parameter of the path-integral approach. In turn, the operator formalism is inconsistent with non-perturbative renormalizability of the massless Thirring model. We carry out a non-perturbative renormalization of the sine-Gordon model and show that it is not an asymptotically free theory as well as the massless Thirring model. We calculate the fermion condensate by using the Fourier transform of the two-point Green function of massless Thirring fermion fields quantized in the chiral symmetric phase.

hep-th↗
arXiv2001

Singularities of ultra-relativistic expanding quark-gluon plasma within Quark-gluon transport theory

We follow Quark-gluon transport theory and analyse singularities of the ultra-relativistic and spherical expanding quark-gluon plasma. Within the linearized QCD oscillations and instabilities of the ultra-relativistic and spherical symmetric expanding quark-gluon plasma near global thermodynamical equilibrium are investigated in dependence on a chemical potential mu(T) of non-strange light quarks and antiquarks, a strange quark mass m_s, a temperature T and a hydrodynamical velocity $u$. We calculate the chromoelectric permeability tensor for the quark-gluon plasma at rest and ultra-relativistic moving. We show that the contribution of chemical potential of light quarks and antiquarks can be neglected to the chromoelectric permeability. We show that the account for the non-zero mass of strange quarks and antiquarks diminishes the value of the plasma frequency. We show that the plasma frequency of the ultra-relativistic and spherical symmetric expanding quark-gluon plasma is enhanced by a Lorentz factor compared with the plasma frequency of the quark-gluon plasma at rest. We find that the ultra-relativistic and spherical symmetric expanding quark-gluon plasma behaves like a collisionless thermalized plasma.

nucl-th↗
arXiv2001

On polarization of strange baryons in reactions p + p -> p + Lambda^0 + K^+ and p + p -> p + Sigma^0 + K^+ near thresholds

Polarization properties of strange baryons produced in pp reactions, p + p -> p + Lambda^0 + K^+ and p + p -> p + Sigma^0 + K^$, near thresholds of the final states (p Lambda^0 K^+) and (p Sigma^0 K^+) are analysed relative to polarizations of colliding protons. The cross sections for pp reactions are calculated within the effective Lagrangian approach accounting for strong pp rescattering in the initial state of colliding protons with a dominant contribution of the one-pion exchange and strong final-state interaction of daughter hadrons (Eur. Phys. J. A 9, 425 (2000)).

nucl-th↗
arXiv2001

On the D-wave state component of the deuteron in the Nambu-Jona-Lasinio model of light nuclei

The D-wave state component of the neutron-proton bound state in the deuteron is calculated in the Nambu-Jona-Lasinio model of light nuclei - the relativistically covariant quantum field theoretic approach to the description of low-energy nuclear forces. The theoretical value of the fraction of the D-wave state relative to the S-wave state is equal to eta_d = 0.0238. This agrees well with the phenomenological value eta_d = 0.0256(4) quoted by Kamionkowski and Bahcall (ApJ. 420, 884 (1994)).

nucl-th↗
arXiv2000

On the path integral representation for Wilson loops and the non-Abelian Stokes theorem II

This paper is a revised version of our recent publication Faber et al., Phys. Rev. D62 (2000) 025019, hep-th/9907048. The main revision concerns the expansion into group characters that we have used for the evaluation of path integrals over gauge degrees of freedom. In the present paper we apply the expansion recommended by Diakonov and Petrov in hep-lat/0008004. Our former expansion was approximate and in the region of the particular values of parameters violated the completeness condition by 1.4%. We show that by using the expansion into characters recommended by Diakonov and Petrov in hep-lat/0008004 our previous results are retained and the path integral over gauge degrees of freedom for Wilson loops derived by Diakonov and Petrov (Phys. Lett. B224 (1989) 131 and hep-lat/0008004) by using a special regularization is erroneous and predicts zero value for the Wilson loop. We give comments on the paper hep-lat/0008004.

hep-th↗
arXiv2000

On the polarization properties of the charmed baryon Lambda^+_c in the Lambda^+_c -> p + K^- + pi^+ + pi^0 decay

The polarization properties of the charmed Lambda^+_c baryon are investigated in weak non-leptonic four-body Lambda^+_c -> p + K^- + pi^+ + pi^0 decay. The probability of this decay and the angular distribution of the probability are calculated in the effective quark model with chiral U(3)XU(3) symmetry incorporating Heavy Quark Effective theory (HQET) and the extended Nambu-Jona-Lasinio model with a linear realization of chiral U(3)XU(3) symmetry. The theoretical value of the probability of the decay Lambda^+_c -> p + K^- + pi^+ + pi^0 relative to the probability of the decay Lambda^+_c -> p + K^- + pi^+ does not contain free parameters and fits well experimental data. The application of the obtained results to the analysis of the polarization of the Lambda^+_c produced in the processes of photo and hadroproduction is discussed.

hep-ph↗
arXiv2000

On the reactions p + p -> p + Lambda + K^+ and p + p -> p + Sigma^0 + K^+ near thresholds

The cross sections for the reactions of the strange production p + p -> p + Lambda + K^+ and p + p -> p + Sigma^0 + K^+ near thresholds of the final states p Lambda K^+ and p Sigma^0 K^+ are calculated in the effective Lagrangian approach. Our approach is based on the dominant contribution of the one-pion exchange and strong interaction of the colliding protons in the initial state. The theoretical values of the cross sections agree reasonably well with the experimental data. The polarization properties of the Lambda and Sigma^0 hyperons are discussed.

hep-ph↗
arXiv2000

On the hadron production from the quark-gluon plasma phase in ultra-relativistic heavy-ion collisions

We describe the quark gluon plasma (QGP) as a thermalized quark-gluon system, the thermalized QGP phase of QCD. The hadronization of the thermalized QGP phase is given in a way resembling a coalescence model with correlated quarks and anti-quarks. The input parameters of the approach are the spatial volumes of the hadronization. We introduce three dimensionless parameters C_M, C_B and C_\bar{B} related to the spatial volumes of the production of low-lying mesons (M), baryons (B) and antibaryons (\bar{B}). We show that at the temperature T= 175 MeV our predictions for the ratios of multiplicities agree good with the presently available set of hadron ratios measured for various experiments given by NA44, NA49, NA50 and WA97 Collaborations on Pb+Pb collisions at 158 GeV/nucleon, NA35 Collaboration on S+S collisions and NA38 Collaboration on O+U and S+U collisions at 200 GeV/nucleon.

hep-ph↗
arXiv2000

Dynamics of low-energy nuclear forces and Solar Neutrino Problems in the Nambu-Jona-Lasinio model of light nuclei

The Solar Neutrino Problems (SNP's) are analysed in the Nambu-Jona-Lasinio model of light nuclei. In this model a possible clue to the solution of the SNP's is in the reduction of the solar neutrino fluxes relative to the predicted by the Standard Solar Model through the decrease of the solar core temperature. The former can be realized through the enhancement of the astrophysical factor for the solar proton burning. The enhancement the upper bound of which is restricted by the helioseismological data goes dynamically via the contribution of the nucleon tensor current coupled to the deuteron. The agreement of the reduced solar neutrino fluxes with the experimental data can be reached within a scenario of vacuum two-flavour neutrino oscillations without a fine tuning of the neutrino-flavour oscillation parameters. In the Nambu-Jona-Lasinio model of light nuclei an enhancement of the astrophysical factor for the solar proton burning entails a change of the cross sections for neutrino and anti-neutrino disintegration of the deuteron at low energies. This provides a theoretical foundation for a new check of a value of the astrophysical factor in terrestrial laboratories.

astro-ph↗
arXiv2000

On the Delta-Delta component of the deuteron in the Nambu-Jona-Lasinio model of light nuclei

The probability P(Delta-Delta) to find the Delta-Delta component inside the deuteron, where Delta stands for the Delta(1232) resonance, is calculated in the Nambu-Jona-Lasinio model of light nuclei. We obtain P(Delta-Delta) = 0.3%. This prediction agrees good with the experimental estimate P(Delta-Delta) < 0.4% at 90% of CL (D. Allasia et al., Phys. Lett. B174 (1986) 450).

nucl-th↗
arXiv2000

The Nambu-Jona-Lasinio model of light nuclei

The Nambu-Jona-Lasinio model of the deuteron suggested by Nambu and Jona-Lasinio (Phys. Rev. 124 (1961) 246) is formulated from the first principles of QCD. The deuteron appears as a neutron-proton collective excitation, i.e. a Cooper np-pair, induced by a phenomenological local four-nucleon interaction in the nuclear phase of QCD. The model describes the deuteron coupled to itself, nucleons and other particles through one-nucleon loop exchanges providing a minimal transfer of nucleon flavours from initial to final nuclear states and accounting for contributions of nucleon-loop anomalies which are completely determined by one-nucleon loop diagrams. The dominance of contributions of nucleon-loop anomalies to effective Lagrangians of low-energy nuclear interactions is justified in the large N_C expansion, where N_C is the number of quark colours.

nucl-th↗