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Particles, Volume 1, Issue 1 (June 2018)

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Editorial

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Open AccessEditorial Particles: A New International Open Access Journal for Nuclear and Particle Physics
Received: 6 November 2017 / Accepted: 6 November 2017 / Published: 9 November 2017
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Abstract
Particles, a new online, open access journal, has been launched to facilitate the publication of original research papers, review articles, and communications of new results and progress in a broad set of subfields which span nuclear and particle physics, experimental/theoretical high-energy physics
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Particles, a new online, open access journal, has been launched to facilitate the publication of original research papers, review articles, and communications of new results and progress in a broad set of subfields which span nuclear and particle physics, experimental/theoretical high-energy physics and astrophysics.[...] Full article

Research

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Open AccessArticle Relativistic Mean-Field Models with Different Parametrizations of Density Dependent Couplings
Received: 16 January 2018 / Revised: 29 January 2018 / Accepted: 30 January 2018 / Published: 2 February 2018
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Abstract
Relativistic mean-field models are successfully used for the description of finite nuclei and nuclear matter. Approaches with density-dependent meson-nucleon couplings assume specific functional forms and a dependence on vector densities in most cases. In this work, parametrizations with a larger sample of functions
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Relativistic mean-field models are successfully used for the description of finite nuclei and nuclear matter. Approaches with density-dependent meson-nucleon couplings assume specific functional forms and a dependence on vector densities in most cases. In this work, parametrizations with a larger sample of functions and dependencies on vector and scalar densities are investigated. They are obtained from fitting properties of finite nuclei. The quality of the description of nuclei and the obtained equations of state of symmetric nuclear matter and neutron matter below saturation are very similar. However, characteristic nuclear matter parameters, the equations of state and the symmetry energy at suprasaturation densities show some correlations with the choice of the density dependence and functional form of the couplings. Conditions are identified that can lead to problems for some of the parametrizations. Full article
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Open AccessArticle Limits on the Reconstruction of a Single Dark Energy Scalar Field Potential from SNe Ia Data
Received: 27 January 2018 / Revised: 16 February 2018 / Accepted: 22 February 2018 / Published: 28 February 2018
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Abstract
In this paper we perform a reconstruction of the scalar field potential responsible for cosmic acceleration using SNe Ia data. After describing the method, we test it with real SNe Ia data—Union2.1 and JLA SNe datasets. We demonstrate that with the current data
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In this paper we perform a reconstruction of the scalar field potential responsible for cosmic acceleration using SNe Ia data. After describing the method, we test it with real SNe Ia data—Union2.1 and JLA SNe datasets. We demonstrate that with the current data precision level, the full reconstruction is not possible. We discuss the problems which arise during the reconstruction process and the ways to overcome them. Full article
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Open AccessArticle Azimuthal Fermionic Current in the Cosmic String Spacetime Induced by a Magnetic Tube
Received: 23 January 2018 / Revised: 12 March 2018 / Accepted: 12 March 2018 / Published: 16 March 2018
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Abstract
In this paper, we calculate the vacuum expectation value of the azimuthal fermionic current, associated with a massive fermionic quantum field in the spacetime of an idealized cosmic string, considering the presence of a magnetic tube of radius a, coaxial to the
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In this paper, we calculate the vacuum expectation value of the azimuthal fermionic current, associated with a massive fermionic quantum field in the spacetime of an idealized cosmic string, considering the presence of a magnetic tube of radius a, coaxial to the string. In this analysis three distinct configurations of magnetic field are considered: (i) a magnetic field concentrated on a surface of the tube; (ii) a magnetic field presenting a 1 / r radial dependence; and (iii) an homogeneous magnetic field. In order to develop this analysis , we construct the complete set of normalized solution of the Dirac equation in the region outside the tube. By using the mode-sum formula, we show that the azimuthal induced current is formed by two contributions: the first being the current induced by a line of magnetic flux running along the string, and the second, named core-induced current, is induced by the non-vanishing extension of the magnetic tube. The first contribution depends only on the fractional part of the ration of the magnetic flux inside the tube by the quantum one; as to the second contribution, it depends on the total magnetic flux. We specifically analyze the core-induced current in several limits of the parameters and distance to the tube. Full article
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Open AccessArticle Turbulence Generation by Shock-Acoustic-Wave Interaction in Core-Collapse Supernovae
Received: 11 April 2018 / Revised: 30 April 2018 / Accepted: 1 May 2018 / Published: 7 May 2018
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Abstract
Convective instabilities in the advanced stages of nuclear shell burning can play an important role in neutrino-driven supernova explosions. In our previous work, we studied the interaction of vorticity and entropy waves with the supernova shock using a linear perturbations theory. In this
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Convective instabilities in the advanced stages of nuclear shell burning can play an important role in neutrino-driven supernova explosions. In our previous work, we studied the interaction of vorticity and entropy waves with the supernova shock using a linear perturbations theory. In this paper, we extend our work by studying the effect of acoustic waves. As the acoustic waves cross the shock, the perturbed shock induces a field of entropy and vorticity waves in the post-shock flow. We find that, even when the upstream flow is assumed to be dominated by sonic perturbations, the shock-generated vorticity waves contain most of the turbulent kinetic energy in the post-shock region, while the entropy waves produced behind the shock are responsible for most of the density perturbations. The entropy perturbations are expected to become buoyant as a response to the gravity force and then generate additional turbulence in the post-shock region. This leads to a modest reduction of the critical neutrino luminosity necessary for producing an explosion, which we estimate to be less than ~5%. Full article
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Open AccessArticle Some Theoretical Aspects of Magnetars
Received: 31 January 2018 / Revised: 29 April 2018 / Accepted: 4 May 2018 / Published: 9 May 2018
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Abstract
Magnetars have been observationally determined to have surface magnetic fields of order of 10141015 G, and the implied internal field strength may be even larger. We discuss the effect of strong field on the dense matter expected to be
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Magnetars have been observationally determined to have surface magnetic fields of order of 10 14 10 15 G, and the implied internal field strength may be even larger. We discuss the effect of strong field on the dense matter expected to be inside neutron stars. We describe the microphysics, phenomenology, and astrophysical implications of strong field induced unpairing effect that may occur in magnetars, if the local magnetic field in the core of a magnetar exceeds a critical value. The density dependence of the pairing of proton condensate implies that the critical value required for the unpairing effect to occur is maximal at the crust–core interface and decreases towards the center of the star. As a consequence, magnetar cores with homogeneous constant fields will be partially superconducting for “medium-field” magnetars, whereas “strong-field” magnetars will be void of superconductivity. We also discuss its effect on some observational phenomena which depend on the nature and composition of matter inside neutron stars. Full article
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Open AccessArticle Active Oxygen Target for Studies in Nuclear Astrophysics with Laser Compton Backscattered γ-ray Beams
Received: 30 January 2018 / Revised: 16 May 2018 / Accepted: 16 May 2018 / Published: 20 May 2018
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Abstract
An active target is being developed to be used in low-energy nuclear astrophysics experiments. It is a position- and time-sensitive detector system based on the low-pressure Multi Wire Proportional Chamber (MWPC) technique. Methylal ((OCH3)2CH2), at a pressure
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An active target is being developed to be used in low-energy nuclear astrophysics experiments. It is a position- and time-sensitive detector system based on the low-pressure Multi Wire Proportional Chamber (MWPC) technique. Methylal ((OCH3)2CH2), at a pressure of a few Torr, serves as the working gas for MWPC operation, and in addition, the oxygen atoms of the methylal molecules serve as an experimental target. The main advantage of this new target detector system is that it has high sensitivity to the low-energy, highly-ionizing particles produced after photodisintegration of 16O and insensitivity to γ-rays and minimum ionizing particles. This allows users to detect only the products of the nuclear reaction of interest. The threshold energies for detection of α particles and 12C nuclei are about 50 keV and 100 keV, respectively. The main disadvantage of this detector is the small target thickness, which is around a few tens of μg/cm2. However, reasonable luminosity can be achieved by using a multimodule detector system and an intense, Laser Compton Backscattered (LCB) γ-ray beam. This paper summarizes the architecture of the active target and reports test results of the prototype detector. The tests investigated the timing and position resolutions of 30 × 30 mm2 low-pressure MWPC units using an α-particle source. The possibility of measuring the 16O(γ, α)12C cross-section in the 8–10 MeV energy region by using a LCB γ-ray beam is also discussed. A measurement of the 16O(γ, α)12C cross-section will enable the reaction rate of 12C(α, γ)16O to be determined with significantly improved precision compared to previous experiments. Full article
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Open AccessArticle Lorentz Invariance and the Zero-Point Stress-Energy Tensor
Received: 7 April 2018 / Revised: 20 May 2018 / Accepted: 21 May 2018 / Published: 24 May 2018
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Abstract
Some 67 years ago (1951), Wolfgang Pauli noted that the net zero-point energy density could be set to zero by a carefully fine-tuned cancellation between bosons and fermions. In the current article, I will argue in a slightly different direction: the zero-point energy
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Some 67 years ago (1951), Wolfgang Pauli noted that the net zero-point energy density could be set to zero by a carefully fine-tuned cancellation between bosons and fermions. In the current article, I will argue in a slightly different direction: the zero-point energy density is only one component of the zero-point stress energy tensor, and it is this tensor quantity that is in many ways the more fundamental object of interest. I shall demonstrate that Lorentz invariance of the zero-point stress energy tensor implies finiteness of the zero-point stress energy tensor, and vice versa. Under certain circumstances (in particular, but not limited to, the finite quantum field theories (QFTs)), Pauli’s cancellation mechanism will survive the introduction of particle interactions. I shall then relate the discussion to beyond standard model (BSM) physics, to the cosmological constant, and to Sakharov-style induced gravity. Full article

Review

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Open AccessReview Realistic Compactification Models in Einstein–Gauss–Bonnet Gravity
Received: 30 January 2018 / Revised: 15 February 2018 / Accepted: 28 February 2018 / Published: 4 March 2018
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Abstract
We report the results of a study on the dynamical compactification of spatially flat cosmological models in Einstein–Gauss–Bonnet gravity. The analysis was performed in the arbitrary dimension in order to be more general. We consider both vacuum and Λ-term cases. Our results
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We report the results of a study on the dynamical compactification of spatially flat cosmological models in Einstein–Gauss–Bonnet gravity. The analysis was performed in the arbitrary dimension in order to be more general. We consider both vacuum and Λ -term cases. Our results suggest that for vacuum case, realistic compactification into the Kasner (power law) regime occurs with any number of dimensions (D), while the compactification into the exponential solution occurs only for D 2 . For the Λ -term case only compactification into the exponential solution exists, and it only occurs for D 2 as well. Our results, combined with the bounds on Gauss–Bonnet coupling and the Λ -term ( α , Λ , respectively) from other considerations, allow for the tightening of the existing constraints and forbid α < 0 . Full article
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Open AccessReview Scalar Fields as Sources for Wormholes and Regular Black Holes
Received: 1 February 2018 / Revised: 8 March 2018 / Accepted: 9 March 2018 / Published: 14 March 2018
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Abstract
We review nonsingular static, spherically symmetric solutions of general relativity with minimally coupled scalar fields. Considered are wormholes and regular black holes (BHs) without a center, including black universes (BHs with expanding cosmology beyond the horizon). Such configurations require a “ghost” field with
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We review nonsingular static, spherically symmetric solutions of general relativity with minimally coupled scalar fields. Considered are wormholes and regular black holes (BHs) without a center, including black universes (BHs with expanding cosmology beyond the horizon). Such configurations require a “ghost” field with negative kinetic energy K. Ghosts can be invisible under usual conditions if K < 0 only in strong-field region (“trapped ghost”), or they rapidly decay at large radii. Before discussing particular examples, some general results are presented, such as the necessity of anisotropic matter for asymptotically flat or AdS wormholes, no-hair and global structure theorems for BHs with scalar fields. The stability properties of scalar wormholes and regular BHs under spherical perturbations are discussed. It is stressed that the effective potential V eff for perturbations has universal shapes near generic wormhole throats (a positive pole regularizable by a Darboux transformation) and near transition surfaces from canonical to ghost scalar field behavior (a negative pole at which the perturbation finiteness requirement plays a stabilizing role). Positive poles of V eff emerging at “long throats” (with the radius r r 0 + const · x 2 n , n > 1 , x = 0 is the throat) may be regularized by repeated Darboux transformations for some values of n. Full article
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