Results 1 - 10 of 1713
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[en] Lorentz gauge theory of gravity was recently introduced. We study the homogeneous and isotropic universe of this theory. It is shown that some time after the matter in the universe is diluted enough, at , the decelerating expansion shifts spontaneously to an accelerating one without a dark energy. We discuss that Lorentz gauge theory puts no constraint on the total energy content of the universe at present time and therefore the magnitude of vacuum energy predicted by field theory is not contradictory anymore. It is demonstrated that in this theory the limit on the number of relativistic particles in the universe is much looser than in GR. An inflationary mechanism is discussed as well. We show that the theory, unlike GR, does not require the slow-roll or similar conditions to drive the inflation at the beginning of the universe. (paper)
[en] The almost hermetic coverage of the CMS detector is used to measure the distribution of transverse energy, Eτ, over 13.2 units of pseudorapidity η for pPb collisions at a center-of-mass energy per nucleon pair of √sNN=5.02 TeV. The huge angular acceptance exploits the fact that the CASTOR calorimeter at -6.6 < η < -5.2 is effectively present on both sides of the colliding system because of a switch in the proton-going and lead-goingbeam directions. This wide acceptance enables the study of correlations between well-separated angular regionsand makes the measurement a particularly powerful test of event generators. For minimum biaspPb collisionsthe maximum value of dEτ/dη is 22 GeV, which implies an Eτ per participant nucleon pair comparable to thatof peripheral PbPb collisions at √sNN=2.76 TeV. The increase of dEτ/dη with centrality is much stronger forthe lead-going side than for the proton-going side. The η dependence of dEτ/dη is sensitive to the η range inwhich the centrality variable is defined. Several modern generators are compared to these results but none isable to capture all aspects of the η and centrality dependence of the data and the correlations observed between different η regions. © 2019 CERN.
[en] The processes accompanying the interaction (localization) of the particle's Ψ-function cause debates and discussions for a very long time. Let us cite the extract from de Broglie's book. ''As soon as the particle is discovered in the point ''A'', the probability to discover it at any other point ''B'' gets equal to zero, since only one particle is connected with the wave psi''. And further: ''... any of mechanisms, based on the classical or even on relativistic forecasts about the space or time, evidently is not able to explain such an instantaneous squeezing, which is tightly connected with the indivisible character of a particle''. However, it seems to be possible, remaining within the frames of quantum mechanics to build a sufficient logical picture, where these difficulties will be avoided. This consideration is based on the collation of the particle and the wave packet motions and on the possibility of dual description of wave packet, coming from two uncertainties Δx ΔPx ∼ ħ and Δt ΔE ∼ ħ, and was partly stimulated by the mentioned in de Broglie's book. Within the frames of this model, the infinity is removed from the description of collapse process, while the interaction of two elementary particles turns out to be the two stages process. At the first, preliminary stage the object to interact with will be discovered. As a result the symmetry of the system changes, so the second, final stage necessarily proceeds within the frames of Feynman's mechanism of path integrals. (author)
[en] Ground states ofinteracting QFTs are non-Gaussian states, i.e. their connected n-point correlation functions do not vanish for , in contrast to the free QFT case. We show that, when the ground state of an interacting QFT evolves under a free massive QFT for a long time (a scenario that can be realised by a quantum quench), the connected correlation functions decay and all local physical observables equilibrate to values that are given by a Gaussian density matrix that retains memory only of the two-point initial correlation function. The argument hinges upon the fundamental physical principle of cluster decomposition, which is valid for the ground state of a general QFT. An analogous result was already known to be valid in the case of d = 1 spatial dimensions, where it is a special case of the so-called generalised Gibbs ensemble (GGE) hypothesis, and we now generalise it to higher dimensions. Moreover, in the case of massless free evolution, despite the fact that the evolution may lead not to equilibration but instead to unbounded increase of correlations with time, the GGE gives correctly the leading-order asymptotic behaviour of correlation functions in the thermodynamic and large time limit. The demonstration is performed in the context of a bosonic relativistic QFT, but the arguments apply more generally. (paper)
[en] The pairing energy density functionals (EDFs) that include the spatial derivative and kinetic terms of the pair densities are discussed. The coupling constants of the pairing EDF are adjusted to reproduce the experimental pairing rotational moment of inertia, and the pair-density derivative terms are shown to systematically improve the values of the pairing rotational moments of inertia in Sn and Pb isotopes. It is pointed out that the conventional average pairing gaps overestimate the experimental odd–even mass staggering in the presence of the pair-density derivative terms. (paper)
[en] We study the dynamics of a Bose-Einstein condensate subject to a particular Penrose tiling lattice. In such a lattice, the potential energy at each site depends on the neighbour sites, accordingly to the model introduced by Sutherland . The Bose-Einstein wavepacket, initially at rest at the lattice symmetry center, is released. We observe a very complex time-evolution that strongly depends on the symmetry center (two choices are possible), on the potential energy landscape dispersion, and on the interaction strength. The condensate-width oscillates at different frequencies and we can identify large-frequency reshaping oscillations and low-frequency rescaling oscillations. We discuss in which conditions these oscillations are spatially bounded, denoting a self-trapping dynamics.
[en] We study how to efficiently control an interacting few-body system consisting of three harmonically trapped bosons. Specifically, we investigate the process of modulating the inter-particle interactions to drive an initially non-interacting state to a strongly interacting one, which is an eigenstate of a chosen Hamiltonian. We also show that for unbalanced subsystems, where one can individually control the different inter- and intra-species interactions, complex dynamics originate when the symmetry of the ground state is broken by phase separation. However, as driving the dynamics too quickly can result in unwanted excitations of the final state, we optimize the driven processes using shortcuts to adiabaticity, which are designed to reduce these excitations at the end of the interaction ramp, ensuring that the target eigenstate is reached.
[en] The spectrum of the ss¯ mesons is studied performing a phenomenological analysis of the Regge trajectories defined for the excitation energies. For the ϕ(33S1) state the mass M(ϕ(3S))=2100(20) MeV and the leptonic width Γee(ϕ(3S))=0.27(2) keV are obtained, while the mass of the 23D1 state, M(ϕ(23D1))=2180(5) MeV, appears to be in agreement with the mass of the ϕ(2170) resonance, and its leptonic width, Γee(23D1 )=0.20±0.10 keV, has a large theoretical uncertainty, depending on the parameters of the flattened confining potential. (author)
[en] It is generally considered that hadron matter may undergo a deconfinement phase transition becoming quark matter at very high density in massive neutron stars. This hadron-quark phase transition has important impact on neutron stars, which has received much attention. We consider finite-size effect in this phase transition process, which contains the impact of Coulomb energy and surface energy. By including this effect, the mixed phase forms the pasta structures. The equilibrium conditions for coexisting hadronic and quark phases are derived by minimizing the total energy including the surface and Coulomb contributions. We employ the relativistic mean-field(RMF) model to describe the hadronic phase, while the Nambu-Jona-Lasinio(NJL) model is used for the quark phase. We conclude that the finite-size effect will raise the stiffness of EOS, and then increase the maximum mass of neutron stars, which depend on the value of surface tension. Our results show that finite-size effects can significantly reduce the region of the mixed phase, and the results lie between those from the Gibbs and Maxwell constructions. We show that a massive star may contain a mixed phase core and its size depends on the surface tension of the hadron-quark interface. (authors)
[en] A detailed analysis of the proton- and neutron-halo breakup cross sections is presented. Larger neutron-halo breakup cross sections than proton-halo breakup cross sections are obtained. This is found to be mainly due to the projectile structure, namely the ground state wave function and the dipole electric response function. It is also found that the continuum–continuum couplings are stronger in the proton-halo breakup than in the neutron-halo breakup. The increase of proton- and neutron-halo ground state separation energy slightly strengthens these couplings in the proton- and neutron-halo total and nuclear breakups, while they are weakened in the proton- and neutron-halo Coulomb breakups. The Coulomb-nuclear interference remains strongly destructive in both proton- and neutron-halo breakups and this is independent of the ground state separation energy. The results also show that the increase of the neutron-halo ground state separation energy decreases significantly the agreement between the proton- and neutron-halo breakup cross sections, both qualitatively and quantitatively. It is obtained that when the proton-halo ground state separation energy is increased by a factor of 4.380, the proton-halo breakup cross section is reduced by a factor of 4.392, indicating a clear proportionality. However, when the neutron-halo ground state separation energy is increased by the same factor, the neutron-halo total breakup cross section is reduced by a factor of 8.522. (paper)