Search results for "IPA"
showing 10 items of 5795 documents
Systematic approach toβand2νββdecays of massA=100–136nuclei
2015
In this work we perform a systematic study of pairs of single-$\ensuremath{\beta}$-decaying nuclei in the mass region $A=100--136$ to extract information on the effective value of the axial-vector coupling constant ${g}_{\mathrm{A}}$. As the many-body framework we use the quasiparticle random-phase approximation (QRPA) and its proton-neutron variant (pnQRPA) in single-particle valence bases with Woods-Saxon-calculated single-particle energies. It is found that, to a reasonable approximation, ${g}_{\mathrm{A}}$ is a linear function of the mass number $A$, with a slightly different parametrization below and above the mass $A=121$. Using the values of ${g}_{\mathrm{A}}$ extracted from the line…
Unitarity Triangle from CP invariant quantities
2006
We construct the CKM unitarity triangle from CP invariant quantities, using the coupling constant of weak decays with flavor change from b to u, and the particle - antiparticle mixing probability in the B_s and B_d systems. Also included are new measurements of the coupling V_us in Kaon decays. Of the two solutions, one agrees perfectly with the triangle constructed from CP violating processes in the K and B meson systems. The common solution yields a triangle with an area of J/2 = (1.51 +/- 0.09) x 10^{-5} and a CP violating phase gamma = 63.1^o +/- 4.0^o.
Single and double beta decays in the , and triplets of isobars
2014
Abstract In this paper we analyze the ground-state-to-ground-state two-neutrino double beta ( 2 ν β β ) decays and single EC and β − decays for the A = 100 ( 100 Mo– 100 Tc– 100 Ru), A = 116 ( 116 Cd– 116 In– 116 Sn) and A = 128 ( 128 Te– 128 I– 128 Xe) triplets of isobars. We use the proton–neutron quasiparticle random-phase approximation (pnQRPA) with realistic G-matrix-derived effective interactions in very large single-particle bases. The purpose is to access the effective value of the axial-vector coupling constant g A in the pnQRPA calculations. We show that the three triplets of isobars represent systems with different characteristics of orbital occupancies and cumulative 2 ν β β nuc…
Extracting information on the decays from the decays
2005
Abstract We have analyzed the relation between the two-neutrino ( 2 ν β β ) and neutrinoless ( 0 ν β β ) double beta decays of 76Ge, 82Se, 100Mo, and 116Cd. The relevant nuclear matrix elements have been calculated by using the proton–neutron quasiparticle random-phase approximation (pn-QRPA) with realistic two-body interactions. The dependence of the calculated matrix elements on the strength g pp of the particle–particle part of the proton–neutron two-body interaction is investigated. Recently a procedure was proposed where data on 2 ν β β -decay half-lives could be used to derive appropriate values of g pp for calculating the 0 ν β β -decay matrix elements. Following this procedure, we h…
Three-state Landau-Zener model in the presence of dissipation
2019
A population transfer based on adiabatic evolutions in a three-state system undergoing an avoided crossing is considered. The efficiency of the process is analyzed in connection with the relevant parameters, bringing to light an important role of the phases of the coupling constants. The role of dissipation is also taken into account, focusing on external decays that can be described by effective non-Hermitian Hamiltonians. Though the population transfer turns out to be quite sensitive to the decay processes, for very large decay rates the occurrence of a Zeno-phenomenon allows for restoring a very high efficiency.
Modified mode-coupling theory for the collective dynamics of simple liquids
2011
Recently it has been shown that mode-coupling theory, which accounts for the salient features of glassy relaxation near the liquid–glass transition, is also capable of describing the collective excitations of simple liquids away from the glass transition. In order to further improve the agreement between theory and computer simulations on Lennard-Jones argon we modify MCT by taking binary collisions into account. This, in fact, improves the agreement. We also show that multiplying the memory function of the original theory with a reduction factor leads to similar results.
Coupling Mechanics of Antikythera Gearwheels
2012
This paper discusses the gear coupling mechanics of the ancient Antikythera mechanism, among whose distinctive characteristics was the triangular shaping of the teeth. The engagement of the tooth pairs is analyzed in detail, estimating the temporal variation of the speed ratio due to the back and forth shifting of the relative instant center. The admissibility of the theoretical contact points is carefully checked, and the magnitude of the successive tooth collisions is calculated together with the energy losses arising from the particular nature of the coupling. Some interesting results are that only one tooth pair turns out to be active at each time instant and the real path may belong on…
Fine tuning of the magnetic properties in Mn3-Co Ga Heusler films near the critical regime
2021
Abstract Tunability of structural and magnetic properties of Mn3-xCoxGa films is presented by Co substitution, where critical behavior emerges 0.37 ≤ x ≤ 0.56 exhibiting a transition from tetragonal hard ferrimagnetic with perpendicular magnetic anisotropy (PMA) to a cubic soft ferrimagnetic phase with in-plane magnetic anisotropy (IMA). In the critical regime, coexisting state of tetragonal and cubic phases possesses significantly low coercive field (HC = 1.9 kOe) with relatively low saturation magnetization (MS = 100~150 emu/cc) while maintaining the PMA. From first-principles calculations, moments of two Mn sites do not change upon Co substitution. However, moments of substituted Co almo…
Boundary controlled irreversible port-Hamiltonian systems
2021
Abstract Boundary controlled irreversible port-Hamiltonian systems (BC-IPHS) defined on a 1-dimensional spatial domain are defined by extending the formulation of reversible BC-PHS to irreversible thermodynamic systems controlled at the boundaries of their spatial domain. The structure of BC-IPHS has clear physical interpretation, characterizing the coupling between energy storing and energy dissipating elements. By extending the definition of boundary port variables of BC-PHS to deal with the irreversible energy dissipation, a set of boundary port variables are defined such that BC-IPHS are passive with respect to a given set of conjugated inputs and outputs. As for finite dimensional IPHS…
Optomechanical Rydberg-atom excitation via dynamic Casimir-Polder coupling
2014
We study the optomechanical coupling of a oscillating effective mirror with a Rydberg atomic gas, mediated by the dynamical atom-mirror Casimir-Polder force. This coupling may produce a near-field resonant atomic excitation whose probability scales as $\propto (d^2\;a\;n^4\;t)^2/z_0^8$, where $z_0$ is the average atom-surface distance, $d$ the atomic dipole moment, $a$ the mirror's effective oscillation amplitude, $n$ the initial principal quantum number, and $t$ the time. We propose an experimental configuration to realize this system with a cold atom gas trapped at a distance $\sim 2\cdot10 \, \mu$m from a semiconductor substrate, whose dielectric constant is periodically driven by an ext…