Spin polarized neutron matter within the Dirac-Brueckner-Hartree-Fock approach

The relation between energy and density (known as the nuclear equation of state) plays a major role in a variety of nuclear and astrophysical systems. Spin and isospin asymmetries can have a dramatic impact on the equation of state and possibly alter its stability conditions. An example is the possible manifestation of ferromagnetic instabilities, which would indicate the existence, at a certain density, of a spin-polarized state with lower energy than the unpolarized one. This issue is being discussed extensively in the literature and the conclusions are presently very model dependent. We will report and discuss our recent progress in the study of spin-polarized neutron matter. The approach we take is microscopic and relativistic. The calculated neutron matter properties are derived from realistic nucleon-nucleon interactions. This makes it possible to understand the nature of the EOS properties in terms of specific features of the nuclear force model.Comment: 6 pages, 11 figures, revised/extended calculation

Multipair contributions to the spin response of nuclear matter

We analyse the effect of non-central forces on the magnetic susceptibility of degenerate Fermi systems. These include the presence of contributions from transitions to states containing more than one quasiparticle-quasihole pair, which cannot be calculated within the framework of Landau Fermi-liquid theory, and renormalization of the quasiparticle magnetic moment, as well as explicit non-central contributions to the quasiparticle interaction. Consequently, the relationship between the Landau parameters and the magnetic susceptibility for Fermi systems with non-central forces is considerably more complicated than for systems with central forces. We use sum-rule arguments to place a lower bound on the contribution to the static susceptibility coming from transitions to multipair states

Competition of ferromagnetic and antiferromagnetic spin ordering in nuclear matter

In the framework of a Fermi liquid theory it is considered the possibility of ferromagnetic and antiferromagnetic phase transitions in symmetric nuclear matter with Skyrme effective interaction. The zero temperature dependence of ferromagnetic and antiferromagnetic spin polarization parameters as functions of density is found for SkM$^*$, SGII effective forces. It is shown that in the density domain, where both type of solutions of self--consistent equations exist, ferromagnetic spin state is more preferable than antiferromagnetic one.Comment: 9p., 3 figure

Spin susceptibility of neutron matter at zero temperature

The Auxiliary Field Diffusion Monte Carlo method is applied to compute the spin susceptibility and the compressibility of neutron matter at zero temperature. Results are given for realistic interactions which include both a two-body potential of the Argonne type and the Urbana IX three-body potential. Simulations have been carried out for about 60 neutrons. We find an overall reduction of the spin susceptibilty by about a factor 3 with respect to the Pauli susceptibility for a wide range of densities. Results for the compressibility of neutron matter are also presented and compared with other available estimates obtained for semirealistic nucleon-nucleon interactions by using other techniques

Threshold eta and eta' electroproduction off nucleons

The electroproduction of eta and eta' mesons on the proton and the neutron is investigated at tree level within the framework of U(3) chiral perturbation theory. In addition to the Born terms low-lying resonances such as the vector mesons and J^P= 1/2^+, 1/2^- baryon resonances are included explicitly and their contributions are calculated. Results for the separated differential cross sections are presented.Comment: 24 pages, 7 figure

Anisotropic pressure in dense neutron matter under the presence of a strong magnetic field

Dense neutron matter with recently developed BSk19 and BSk21 Skyrme effective forces is considered in magnetic fields up to $10^{20}$ G at zero temperature. The breaking of the rotational symmetry by the magnetic field leads to the differentiation between the pressures along and perpendicular to the field direction which becomes significant in the fields $H>H_{th}\sim10^{18}$ G. The longitudinal pressure vanishes in the critical field $10^{18}<H_c\lesssim10^{19}$ G, resulting in the longitudinal instability of neutron matter. For the Skyrme force fitted to the stiffer underlying equation of state (BSk21 vs. BSk19) the threshold $H_{th}$ and critical $H_c$ magnetic fields become larger. The longitudinal and transverse pressures as well as the anisotropic equation of state of neutron matter are determined under the conditions relevant for the cores of magnetars.Comment: 7 pages, 3 figures; published online 7 December 201

Equation of state and magnetic susceptibility of spin polarized isospin asymmetric nuclear matter

Properties of spin polarized isospin asymmetric nuclear matter are studied within the framework of the Brueckner--Hartree--Fock formalism. The single-particle potentials of neutrons and protons with spin up and down are determined for several values of the neutron and proton spin polarizations and the asymmetry parameter. It is found an almost linear and symmetric variation of the single-particle potentials as increasing these parameters. An analytic parametrization of the total energy per particle as a function of the asymmetry and spin polarizations is constructed. This parametrization is employed to compute the magnetic susceptibility of nuclear matter for several values of the asymmetry from neutron to symmetric matter. The results show no indication of a ferromagnetic transition at any density for any asymmetry of nuclear matter.Comment: 23 pages, 8 figures, 2 tables (submitted to Phys. Rev. C

Phase transition to the state with nonzero average helicity in dense neutron matter

The possibility of the appearance of the states with a nonzero average helicity in neutron matter is studied in the model with the Skyrme effective interaction. By providing the analysis of the self-consistent equations at zero temperature, it is shown that neutron matter with the Skyrme BSk18 effective force undergoes at high densities a phase transition to the state in which the degeneracy with respect to helicity of neutrons is spontaneously removed.Comment: 4 pages, 3 figures; v2: journal versio

Pairing in nuclear systems: from neutron stars to finite nuclei

We discuss several pairing-related phenomena in nuclear systems, ranging from superfluidity in neutron stars to the gradual breaking of pairs in finite nuclei. We focus on the links between many-body pairing as it evolves from the underlying nucleon-nucleon interaction and the eventual experimental and theoretical manifestations of superfluidity in infinite nuclear matter and of pairing in finite nuclei. We analyse the nature of pair correlations in nuclei and their potential impact on nuclear structure experiments. We also describe recent experimental evidence that points to a relation between pairing and phase transitions (or transformations) in finite nuclear systems. Finally, we discuss recent investigations of ground-state properties of random two-body interactions where pairing plays little role although the interactions yield interesting nuclear properties such as 0+ ground states in even-even nuclei.Comment: 74 pages, 33 figs, uses revtex4. Submitted to Reviews of Modern Physic

Tutkinta-arestin edellytykset ja sisältö

Oikeusministeriön tutkintavankeuden vaihtoehtoja selvittänyt työryhmä perustettiin vuonna 2014. Selvityksen taustalla olivat muun muassa useat kansainväliset sopimukset ja suositukset, syyttömyysolettama sekä tutkintavankien määrän lisääntyminen Suomen vankiloissa. Työryhmän selvityksen perusteella pakkokeinolakia uudistettiin ottamalla käyttöön tutkinta-aresti vuoden 2019 alussa. Tässä opinnäytetyössä käsiteltiin lyhyesti pakkokeinolain muutoksen taustaa, perehdyttiin yleisellä tasolla rikosprosessuaalisiin pakkokeinoihin ja tutkintavankeuteen sekä syvennyttiin tutkinta-arestin edellytyksiä ja sisältöä koskevaan lainsäädäntöön. Opinnäytetyössä selvitettiin, milloin ehdottomaan vankeusrangaistukseen tuomittu voidaan määrätä tutkinta-arestiin ja miten se rajoittaa tuomitun vapautta. Tutkinta-aresti on teknisillä laitteilla valvottu pakkokeino, johon alle kahden vuoden pituiseen ehdottomaan vankeusrangaistukseen tuomittu voidaan määrätä vangitsemisen tai vangittuna pitämisen sijasta pakkokeinolaissa määritellyin edellytyksin. Tutkinta-arestin sisältöön kuuluvat asunnossa pysymisvelvollisuus, liikkumisrajoitukset ja tekninen valvonta rajoittavat yksilön henkilökohtaista vapautta ja koskemattomuutta sekä liikkumisvapautta. Tutkimusaiheesta koottiin selkeä kokonaiskuva käräjä- ja hovioikeuksien henkilökunnalle sekä muille asiasta kiinnostuneille. Opinnäytetyö toteutettiin pääasiassa lainopillisena tutkimuksena. Käytännön näkökulmaa opinnäytetyöhön tuotiin asiantuntijahaastatteluiden avulla. Haastattelut toteutettiin kvalitatiivisella tutkimusotteella.In 2014 a working group was set up by the Ministry of Justice to explore the alternatives to remand imprisonment. The underlying causes for the survey included e.g. international agreements and recommendations, presumption of innocence and the increase in the number of prisoners on remand in Finnish prisons. Based on the survey of the working group, Coercive Measures Act was reformed by adopting remand arrest at the beginning of year 2019. In this Bachelor´s thesis the background to amendment in Coercive Measures Act was discussed, coercive means in criminal procedure and remand imprisonment were studied at a general level, and the legislation related to the preconditions and contents of remand arrest was researched more in detail. In the thesis it was clarified when a person sentenced to unconditional sentence of imprisonment can be ordered to remand arrest and how it restricts the freedom of the sentenced person. Remand arrest is a technically monitored coercive measure, which a person sentenced to less than two years of unconditional sentence of imprisonment can be sentenced to instead of imprisonment or detention under the preconditions defined in the act. The contents of the remand arrest including the obligation to stay at home, movement restrictions and technical monitoring restrict the person´s personal freedom and integrity as well as freedom of movement. A clear overall view of the research subject was compiled for the district court and court of appeal personnel as well as others interested in the subject. The thesis was mainly carried out as a juridical research. A practical perspective for the thesis was introduced by expert interviews. The interviews were conducted by using a qualitative research approach