Dubravko Horvat - Academia.edu (original) (raw)
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Papers by Dubravko Horvat
This paper is a continuation of an earlier paper on hypernuclear potentials. A novel derivation o... more This paper is a continuation of an earlier paper on hypernuclear potentials. A novel derivation of the hypernuclear strangeness-violating potential due to the pseudoscalar meson exchanges is presented. Comparison with the earlier method shows that the theoretical uncertainty is less than 30%. Relative signs of pseudoscalar meson exchanges and vector (axial vector) exchanges are discussed in detail. Additional comments on the nonrelativistic approximation are included.
The notion of a compact object immune to the horizon problem and comprising an anisotropic inhomo... more The notion of a compact object immune to the horizon problem and comprising an anisotropic inhomogeneous fluid with a specific radial pressure behavior, i.e. the gravastar, is extended by introducing an electrically charged component. Einstein-Maxwell field equations are solved in the asymptotically de Sitter interior where a source of the electric field is coupled to the fluid energy density. Two different solutions which satisfy the dominant energy condition are given: one is the δ-shell model for which the analysis is carried out within Israel's thin shell formalism, the other approach-the continuous profile model-is solved numerically and the interior solutions have been (smoothly) joined with the Reissner-Nordström exterior. The effect of electric charge is considered, and the equation of state, the speed of sound and the surface redshift are calculated for both models.
Fizika 2, Pojmovi i koncepti, zbirka zadataka za 2. razred cetverogodisnjih strukovnih skola s ce... more Fizika 2, Pojmovi i koncepti, zbirka zadataka za 2. razred cetverogodisnjih strukovnih skola s cetverogodisnjim ucenjem fizike
Udžbenik s multimedijskim sadržajem za 2. razred cetverogodisnjih strukovnih skola s cetverogodis... more Udžbenik s multimedijskim sadržajem za 2. razred cetverogodisnjih strukovnih skola s cetverogodisnjim ucenjem fizike
Radna bilježnica za 1. razred cetverogodisnjih strukovnih skola s cetverogodisnjim ucenjem fizike
It is shown that in the simple context of the elementary one-meson exchanges, the use of the &quo... more It is shown that in the simple context of the elementary one-meson exchanges, the use of the "improper" delta "functions" could lead to the physically correct results. The same results were obtained by involving limiting values of the integrals over "proper" functions, thus providing the examples of the sequences connected with delta "functions". That formulation of sequences of integrals emerged automatically from the physical considerations concerning hypernuclear processes.
arXiv: High Energy Physics - Phenomenology, 2000
The pieces of the hypernuclear strangeness violating potential due to the pseudoscalar meson exch... more The pieces of the hypernuclear strangeness violating potential due to the pseudoscalar meson exchanges are derived using methods which were successfully applied to hyperon nonleptonic decays. The estimates are tested by comparison with measured hyperon nonleptonic decay amplitudes. All isospin changes DeltaI=1/2\Delta I=1/2DeltaI=1/2 and DeltaI=3/2\Delta I=3/2DeltaI=3/2 are included in the derived potential. All calculational methods used are reviewed and described in detail.
Classical and Quantum Gravity, 2009
The notion of a compact object immune to the horizon problem and comprising an anisotropic inhomo... more The notion of a compact object immune to the horizon problem and comprising an anisotropic inhomogeneous fluid with a specific radial pressure behavior, i.e. the gravastar, is extended by introducing an electrically charged component. Einstein-Maxwell field equations are solved in the asymptotically de Sitter interior where a source of the electric field is coupled to the fluid energy density. Two different solutions which satisfy the dominant energy condition are given: one is the δ-shell model for which the analysis is carried out within Israel's thin shell formalism, the other approach-the continuous profile model-is solved numerically and the interior solutions have been (smoothly) joined with the Reissner-Nordström exterior. The effect of electric charge is considered, and the equation of state, the speed of sound and the surface redshift are calculated for both models.
The chiral sigma model, embedded in the chiral-bag environment, is solved by an ansatz which cons... more The chiral sigma model, embedded in the chiral-bag environment, is solved by an ansatz which conserves isospin and spin separably. This chiral ansatz is treated in two ways: i) as a set of operator equations of motion solved between quark states and ii) the hamilton operator is averaged between suitable hadron states, and the equations of motion are derived for these mean fields. The second approach is completely analogous to the usual one which employs hedgehog quarks, which is also reproduced here. It turns out that the energy minimum (i.e. hadron masses) can be found with chiral quarks as well as with hedgehog quarks. Model predictions for the axial-vector coupling constant and for the nucleon magnetic moment obtained with chiral quarks are of the same quality, or better than those obtained using the usual hedgehog-based approximation.
Canadian Journal of Physics
Solutions for the static spherically symmetric extremally charged dust in the Majumdar–Papapetrou... more Solutions for the static spherically symmetric extremally charged dust in the Majumdar–Papapetrou system have been found. For a certain amount of the allocated mass and (or) charge, the solutions have singularities of a type that could render them physically unacceptable, since the corresponding physically relevant quantities are singular as well. These solutions, with a number of zero-nodes in the metric tensor, are regularized through the δ-shell formalism, thus redefining the mass and (or) charge distributions. The bifurcating behaviour of regular solutions found before is no longer present in these singular solutions, but quantized-like behaviour in the total mass is observed. The spectrum of regularized solutions restores the equality of the Tolman–Whittaker and Arnowitt–Deser–Misner (ADM) mass, as well the equality of the net charge and ADM mass, which is the distinctive feature of Majumdar–Papapetrou systems.PACS No.:04.40.Nr
The chiral sigma model, embedded in the chiral-bag environment, is solved by an ansatz which cons... more The chiral sigma model, embedded in the chiral-bag environment, is solved by an ansatz which conserves isospin and spin separably. This chiral ansatz is treated in two ways: i) as a set of operator equations of motion solved between quark states and ii) the hamilton operator is averaged between suitable hadron states, and the equations of motion are derived for these mean fields. The second approach is completely analogous to the usual one which employs hedgehog quarks, which is also reproduced here. It turns out that the energy minimum (i.e. hadron masses) can be found with chiral quarks as well as with hedgehog quarks. Model predictions for the axial-vector coupling constant and for the nucleon magnetic moment obtained with chiral quarks are of the same quality, or better than those obtained using the usual hedgehog-based approximation.
![Research paper thumbnail of Classical SU(3) Yang-Mills gauge theory with external static sources [microform] /](https://attachments.academia-assets.com/70542771/thumbnails/1.jpg)
](~err&ssion is granted to the fVAT4ONAL LI& OF L'eutorisation est, p8r 18 prbsente, sccordde d I8 ... more ~err&ssion is granted to the fVAT4ONAL LI& OF L'eutorisation est, p8r 18 prbsente, sccordde d I8 BIBLIOTH~-Y CANADA to micrdilrn this thesis end to lend or sell copies OUE NATIONALE DU CANADA de micrdilmer cette thbse et f ,. d the film. 1 de prdter w de vendre des exemplrires du film. 4 'Jhe author resarws other pub1 icetion rights, and w i t her the L'suteur se rdserve les sutres doits de publication; ni /a thesis nor-extensive ts frbn i t m y be p r i n t d or dherthesen; de longs extraits de cells-ci ns doivent &re imprids-wise reproduced witbot.dm mthor's mitten prrnissi&. ou sutrement reproduits sans /'autori&tim Bcrite de /'auteur.
A version of the chiral bag model, which contains the linear σ model dynamics and is quantized by... more A version of the chiral bag model, which contains the linear σ model dynamics and is quantized by using the constituent quark operators, has been solved using a Tamm-Dancoff inspired approximation. Model gives reasonable values for the axial coupling constant g A
ABSTRACT The mesonic sector of the standard chiral bag model was enlarged to include the vector a... more ABSTRACT The mesonic sector of the standard chiral bag model was enlarged to include the vector and axial vector components. New model openly displays the current field identities. It's predictions are close to the older model. This seems to be the consequence of the chiral invariance and of the PCAC and CVC constraints. Particle masses, the axial-vector coupling constant, the proton magnetic moment and the charge radius have been calculated.
Classical and Quantum Gravity, 2015
We study the nonminimally coupled complex scalar field within the framework of teleparallel gravi... more We study the nonminimally coupled complex scalar field within the framework of teleparallel gravity. Coupling of the field nonminimally to the torsion scalar destroys the Lorentz invariance of the theory in the sense that the resulting equations of motion depend on the choice of a tetrad. For the assumed static spherically symmetric spacetime, we find a tetrad which leads to a self-consistent set of equations, and we construct the self-gravitating configurations of the scalar field-boson stars. The resulting configurations develop anisotropic principal pressures and satisfy the dominant energy condition. An interesting property of the configurations obtained with sufficiently large field-to-torsion coupling constant is the outwardly increasing energy density, followed by an abrupt drop towards the usual asymptotic tail. This feature is not present in the boson stars with the field minimally or nonminimally coupled to the curvature scalar, and therefore appears to be a torsion-only effect.
This paper is a continuation of an earlier paper on hypernuclear potentials. A novel derivation o... more This paper is a continuation of an earlier paper on hypernuclear potentials. A novel derivation of the hypernuclear strangeness-violating potential due to the pseudoscalar meson exchanges is presented. Comparison with the earlier method shows that the theoretical uncertainty is less than 30%. Relative signs of pseudoscalar meson exchanges and vector (axial vector) exchanges are discussed in detail. Additional comments on the nonrelativistic approximation are included.
The notion of a compact object immune to the horizon problem and comprising an anisotropic inhomo... more The notion of a compact object immune to the horizon problem and comprising an anisotropic inhomogeneous fluid with a specific radial pressure behavior, i.e. the gravastar, is extended by introducing an electrically charged component. Einstein-Maxwell field equations are solved in the asymptotically de Sitter interior where a source of the electric field is coupled to the fluid energy density. Two different solutions which satisfy the dominant energy condition are given: one is the δ-shell model for which the analysis is carried out within Israel's thin shell formalism, the other approach-the continuous profile model-is solved numerically and the interior solutions have been (smoothly) joined with the Reissner-Nordström exterior. The effect of electric charge is considered, and the equation of state, the speed of sound and the surface redshift are calculated for both models.
Fizika 2, Pojmovi i koncepti, zbirka zadataka za 2. razred cetverogodisnjih strukovnih skola s ce... more Fizika 2, Pojmovi i koncepti, zbirka zadataka za 2. razred cetverogodisnjih strukovnih skola s cetverogodisnjim ucenjem fizike
Udžbenik s multimedijskim sadržajem za 2. razred cetverogodisnjih strukovnih skola s cetverogodis... more Udžbenik s multimedijskim sadržajem za 2. razred cetverogodisnjih strukovnih skola s cetverogodisnjim ucenjem fizike
Radna bilježnica za 1. razred cetverogodisnjih strukovnih skola s cetverogodisnjim ucenjem fizike
It is shown that in the simple context of the elementary one-meson exchanges, the use of the &quo... more It is shown that in the simple context of the elementary one-meson exchanges, the use of the "improper" delta "functions" could lead to the physically correct results. The same results were obtained by involving limiting values of the integrals over "proper" functions, thus providing the examples of the sequences connected with delta "functions". That formulation of sequences of integrals emerged automatically from the physical considerations concerning hypernuclear processes.
arXiv: High Energy Physics - Phenomenology, 2000
The pieces of the hypernuclear strangeness violating potential due to the pseudoscalar meson exch... more The pieces of the hypernuclear strangeness violating potential due to the pseudoscalar meson exchanges are derived using methods which were successfully applied to hyperon nonleptonic decays. The estimates are tested by comparison with measured hyperon nonleptonic decay amplitudes. All isospin changes DeltaI=1/2\Delta I=1/2DeltaI=1/2 and DeltaI=3/2\Delta I=3/2DeltaI=3/2 are included in the derived potential. All calculational methods used are reviewed and described in detail.
Classical and Quantum Gravity, 2009
The notion of a compact object immune to the horizon problem and comprising an anisotropic inhomo... more The notion of a compact object immune to the horizon problem and comprising an anisotropic inhomogeneous fluid with a specific radial pressure behavior, i.e. the gravastar, is extended by introducing an electrically charged component. Einstein-Maxwell field equations are solved in the asymptotically de Sitter interior where a source of the electric field is coupled to the fluid energy density. Two different solutions which satisfy the dominant energy condition are given: one is the δ-shell model for which the analysis is carried out within Israel's thin shell formalism, the other approach-the continuous profile model-is solved numerically and the interior solutions have been (smoothly) joined with the Reissner-Nordström exterior. The effect of electric charge is considered, and the equation of state, the speed of sound and the surface redshift are calculated for both models.
The chiral sigma model, embedded in the chiral-bag environment, is solved by an ansatz which cons... more The chiral sigma model, embedded in the chiral-bag environment, is solved by an ansatz which conserves isospin and spin separably. This chiral ansatz is treated in two ways: i) as a set of operator equations of motion solved between quark states and ii) the hamilton operator is averaged between suitable hadron states, and the equations of motion are derived for these mean fields. The second approach is completely analogous to the usual one which employs hedgehog quarks, which is also reproduced here. It turns out that the energy minimum (i.e. hadron masses) can be found with chiral quarks as well as with hedgehog quarks. Model predictions for the axial-vector coupling constant and for the nucleon magnetic moment obtained with chiral quarks are of the same quality, or better than those obtained using the usual hedgehog-based approximation.
Canadian Journal of Physics
Solutions for the static spherically symmetric extremally charged dust in the Majumdar–Papapetrou... more Solutions for the static spherically symmetric extremally charged dust in the Majumdar–Papapetrou system have been found. For a certain amount of the allocated mass and (or) charge, the solutions have singularities of a type that could render them physically unacceptable, since the corresponding physically relevant quantities are singular as well. These solutions, with a number of zero-nodes in the metric tensor, are regularized through the δ-shell formalism, thus redefining the mass and (or) charge distributions. The bifurcating behaviour of regular solutions found before is no longer present in these singular solutions, but quantized-like behaviour in the total mass is observed. The spectrum of regularized solutions restores the equality of the Tolman–Whittaker and Arnowitt–Deser–Misner (ADM) mass, as well the equality of the net charge and ADM mass, which is the distinctive feature of Majumdar–Papapetrou systems.PACS No.:04.40.Nr
The chiral sigma model, embedded in the chiral-bag environment, is solved by an ansatz which cons... more The chiral sigma model, embedded in the chiral-bag environment, is solved by an ansatz which conserves isospin and spin separably. This chiral ansatz is treated in two ways: i) as a set of operator equations of motion solved between quark states and ii) the hamilton operator is averaged between suitable hadron states, and the equations of motion are derived for these mean fields. The second approach is completely analogous to the usual one which employs hedgehog quarks, which is also reproduced here. It turns out that the energy minimum (i.e. hadron masses) can be found with chiral quarks as well as with hedgehog quarks. Model predictions for the axial-vector coupling constant and for the nucleon magnetic moment obtained with chiral quarks are of the same quality, or better than those obtained using the usual hedgehog-based approximation.
~err&ssion is granted to the fVAT4ONAL LI& OF L'eutorisation est, p8r 18 prbsente, sccordde d I8 ... more ~err&ssion is granted to the fVAT4ONAL LI& OF L'eutorisation est, p8r 18 prbsente, sccordde d I8 BIBLIOTH~-Y CANADA to micrdilrn this thesis end to lend or sell copies OUE NATIONALE DU CANADA de micrdilmer cette thbse et f ,. d the film. 1 de prdter w de vendre des exemplrires du film. 4 'Jhe author resarws other pub1 icetion rights, and w i t her the L'suteur se rdserve les sutres doits de publication; ni /a thesis nor-extensive ts frbn i t m y be p r i n t d or dherthesen; de longs extraits de cells-ci ns doivent &re imprids-wise reproduced witbot.dm mthor's mitten prrnissi&. ou sutrement reproduits sans /'autori&tim Bcrite de /'auteur.
A version of the chiral bag model, which contains the linear σ model dynamics and is quantized by... more A version of the chiral bag model, which contains the linear σ model dynamics and is quantized by using the constituent quark operators, has been solved using a Tamm-Dancoff inspired approximation. Model gives reasonable values for the axial coupling constant g A
ABSTRACT The mesonic sector of the standard chiral bag model was enlarged to include the vector a... more ABSTRACT The mesonic sector of the standard chiral bag model was enlarged to include the vector and axial vector components. New model openly displays the current field identities. It's predictions are close to the older model. This seems to be the consequence of the chiral invariance and of the PCAC and CVC constraints. Particle masses, the axial-vector coupling constant, the proton magnetic moment and the charge radius have been calculated.
Classical and Quantum Gravity, 2015
We study the nonminimally coupled complex scalar field within the framework of teleparallel gravi... more We study the nonminimally coupled complex scalar field within the framework of teleparallel gravity. Coupling of the field nonminimally to the torsion scalar destroys the Lorentz invariance of the theory in the sense that the resulting equations of motion depend on the choice of a tetrad. For the assumed static spherically symmetric spacetime, we find a tetrad which leads to a self-consistent set of equations, and we construct the self-gravitating configurations of the scalar field-boson stars. The resulting configurations develop anisotropic principal pressures and satisfy the dominant energy condition. An interesting property of the configurations obtained with sufficiently large field-to-torsion coupling constant is the outwardly increasing energy density, followed by an abrupt drop towards the usual asymptotic tail. This feature is not present in the boson stars with the field minimally or nonminimally coupled to the curvature scalar, and therefore appears to be a torsion-only effect.