794 research outputs found
The nuclear contacts and short range correlations in nuclei
Atomic nuclei are complex strongly interacting systems and their exact
theoretical description is a long-standing challenge. An approximate
description of nuclei can be achieved by separating its short and long range
structure. This separation of scales stands at the heart of the nuclear shell
model and effective field theories that describe the long-range structure of
the nucleus using a mean- field approximation. We present here an effective
description of the complementary short-range structure using contact terms and
stylized two-body asymptotic wave functions. The possibility to extract the
nuclear contacts from experimental data is presented. Regions in the two-body
momentum distribution dominated by high-momentum, close-proximity, nucleon
pairs are identified and compared to experimental data. The amount of
short-range correlated (SRC) nucleon pairs is determined and compared to
measurements. Non-combinatorial isospin symmetry for SRC pairs is identified.
The obtained one-body momentum distributions indicate dominance of SRC pairs
above the nuclear Fermi-momentum.Comment: Accepted for publication in Physics Letters. 6 pages, 2 figure
Hexagonal Structure of Baby Skyrmion Lattices
We study the zero-temperature crystalline structure of baby Skyrmions by
applying a full-field numerical minimization algorithm to baby Skyrmions placed
inside different parallelogramic unit-cells and imposing periodic boundary
conditions. We find that within this setup, the minimal energy is obtained for
the hexagonal lattice, and that in the resulting configuration the Skyrmion
splits into quarter-Skyrmions. In particular, we find that the energy in the
hexagonal case is lower than the one obtained on the well-studied rectangular
lattice, in which splitting into half-Skyrmions is observed.Comment: RevTeX, 7 pages, 6 figure
Perancangan Aplikasi Travel Guide Objek Wisata Alam Kabupaten Lumajang
Lumajang memiliki banyak objek wisata yang mampu meningkatkan pendapatan daerah Kabupaten Lumajang, selain itu sudah banyak wisatawan asing yang berkunjung, namun hanya mengetahui sedikit objek wisata. Perancangan ini dibuat untuk mengenalkan objek wisata alam yang ada di Kabupaten Lumajang kepada wisatawan mancanegara dan domestik melalui sebuah aplikasi. Aplikasi ini memberikan informasi serta didukung oleh fotografi panorama dan map direction yang selain memberikan informasi, juga mempermudah wisatawan yang ingin berkunjung dan mendalami objek wisata alam yang ada di Kabupaten Lumajang. Melalui perancangan aplikasi ini diharapkan dapat membantu meningkatkan kunjungan wisatawan dan mendongkrak pendapatan daerah Kabupaten Lumajang
Generalized Contact Formalism Analysis of the He Reaction
Measurements of short-range correlations in exclusive He
reactions are analyzed using the Generalized Contact Formalism (GCF). We
consider both instant-form and light-cone formulations with both the AV18 and
local N2LO(1.0) nucleon-nucleon () potentials. We find that kinematic
distributions, such as the reconstructed pair opening angle, recoil neutron
momentum distribution, and pair center of mass motion, as well as the measured
missing energy, missing mass distributions, are all well reproduced by GCF
calculations. The missing momentum dependence of the measured He
/ He cross-section ratios, sensitive to nature of the
interaction at short-distacnes, are also well reproduced by GCF calculations
using either interaction and formulation. This gives credence to the GCF
scale-separated factorized description of the short-distance many-body nuclear
wave-function.Comment: Accepted for publication in Physics Letters B. 8 pages, 4 figures and
online supplementary material
Structural, electronic, and magnetic characteristics of Np_2Co_(17)
A previously unknown neptunium-transition-metal binary compound Np_2Co_(17) has been synthesized and characterized by means of powder x-ray diffraction, ^(237)Np Mössbauer spectroscopy, superconducting-quantum-interference-device magnetometry, and x-ray magnetic circular dichroism (XMCD). The compound crystallizes in a Th_2Ni_(17)-type hexagonal structure with room-temperature lattice parameters α=8.3107(1) Å and c=8.1058(1) Å. Magnetization curves indicate the occurrence of ferromagnetic order below T_C>350 K. Mössbauer spectra suggest a Np^(3+) oxidation state and give an ordered moment of μ_(Np)=1.57(4) μ_B and μ_(Np)=1.63(4) μ_B for the Np atoms located, respectively, at the 2b and 2d crystallographic positions of the P6_3/mmc space group. Combining these values with a sum-rule analysis of the XMCD spectra measured at the neptunium M_(4,5) absorption edges, one obtains the spin and orbital contributions to the site-averaged Np moment [μ_S=−1.88(9) μ_B, μ_L=3.48(9) μ_B]. The ratio between the expectation value of the magnetic-dipole moment and the spin magnetic moment (m_(md)/μS=+1.36) is positive as predicted for localized 5f electrons and lies between the values calculated in intermediate-coupling (IC) and jj approximations. The expectation value of the angular part of the spin-orbit-interaction operator is in excellent agreement with the IC estimate. The ordered moment averaged over the four inequivalent Co sites, as obtained from the saturation value of the magnetization, is μ_(Co)≃1.6 μ_B. The experimental results are discussed against the predictions of first-principles electronic-structure calculations based on the spin-polarized local-spin-density approximation plus the Hubbard interaction
- …