1,449 research outputs found
EXAFS Study on Local Structure of Iron Crystal by the Use of Asymmetrical Monochromator and PSPC
The EXAFS spectroscopy equipment constructed from an asymmetrical cut flat monochromator and PSPC is applied to the structural determination of pure α-iron which has small difference (0.038nm) in the first and second nearest neighbour distance. The efficiency of the curve fitting method for the two shell model of known structure material (α-iron) is discussed, in addition to describing the details of the experimental procedure of our new type of spectrometer and of the EXAFS data analysis
Magnetization plateaus in antiferromagnetic-(ferromagnetic)_{n} polymerized S=1/2 XXZ chains
The plateau-non-plateau transition in the
antiferromagnetic-(ferromagnetic) polymerized XXZ chains under
the magnetic field is investigated. The universality class of this transition
belongs to the Brezinskii-Kosterlitz-Thouless (BKT) type. The critical points
are determined by level spectroscopy analysis of the numerical diagonalization
data for where is the size of a unit cell.
It is found that the critical strength of ferromagnetic coupling decreases with
for small but increases for larger enough . It is also found that
the plateau for large is wide enough for moderate values of exchange
coupling so that it should be easily observed experimentally. This is in
contrast to the plateaus for chains which are narrow for a wide range
of exchange coupling even away from the critical point
The antiferromagnetic order in an F-AF random alternating quantum spin chain : (CH_3)_2 CHNH_3 Cu(Cl_x Br_{1-x})_3
A possibility of the uniform antiferromagnetic order is pointed out in an
S=1/2 ferromagnetic (F) - antiferromagnetic (AF) random alternating Heisenberg
quantum spin chain compound: (CH_3)_2 CHNH_3 Cu(Cl_x Br_{1-x})_3. The system
possesses the bond alternation of strong random bonds that take +/- 2J and weak
uniform AF bonds of -J. In the pure concentration limits, the model reduces to
the AF-AF alternation chain at x=0 and to the F-AF alternation chain at x=1.
The nonequilibrium relaxation of large-scale quantum Monte Carlo simulations
exhibits critical behaviors of the uniform AF order in the intermediate
concentration region, which explains the experimental observation of the
magnetic phase transition. The present results suggest that the uniform AF
order may survive even in the presence of the randomly located ferromagnetic
bonds.Comment: 4 pages, 3 figure
Computing automorphic forms on Shimura curves over fields with arbitrary class number
We extend methods of Greenberg and the author to compute in the cohomology of
a Shimura curve defined over a totally real field with arbitrary class number.
Via the Jacquet-Langlands correspondence, we thereby compute systems of Hecke
eigenvalues associated to Hilbert modular forms of arbitrary level over a
totally real field of odd degree. We conclude with two examples which
illustrate the effectiveness of our algorithms.Comment: 15 pages; final submission to ANTS I
Pengembangan Modul Tata Bahasa Indonesia Berbasis E-learning Untuk Mahasiswa Bipa Tingkat Pemula
Pada mahasiswa BIPA sangat jarang ditemukan bahan ajar yang dapat menunjang pembelajaraan. Begitu pula tidak terjangkaunya kelas pembelajaran disebabkan oleh permasalahan jarak. Sehingga modul berbasis e-learning merupakan jawaban dari permasalahan jarak pada pembelajaran. Penelitian ini bertujuan untuk mengembangkan modul tata bahasa Indonesia untuk BIPA tingkat pemula yang dirinci menjadi pendeskripsian pengembangan modul dan pendeskripsian kualitas modul yang didasarkan pada produk dan pengguna. Penelitian ini merupakan penelitian pengembangan dan produk yang dikembangkan berupa modul tata bahasa Indonesia berbasis e-learning untuk mahaasiswa BIPA tingkat pemula. Model pengembangan ini menggunakan model Four D Model (define, design, develop, disseminate) yang dikembangan oleh Thiagarajan, namun penelitian ini hanya sampai tahap pengembangan saja. Hasil penelitian ini adalah pengembangan modul tata bahasa untuk BIPA tingkat pemula. Penulisan dan penyusunan modul ini berdasarkan pada kurikulum BPKLN (Biro Perencanaan Kerjasama Luar Negeri) dan saran dari validator. Penilaian presentase pada penelitian ini mengadaptasi interval presentase Ratumanan (2011:34). Hasil rekapitulasi rata-rata kualitas modul uji I pada skor 3,5, uji II pada skor 4,2, dan rata-rata 3,9. Dapat dikatakan kualitas modul Baik. Respon dosen pada modul pada skor rata-rata 4,2 yang dapat dikatakan Baik. Aktivitas dan respon mahasiswa uji coba I pada skor 4,3, uji coba II pada skor 4,8, dan rata-rata 4,5 dalam hal ini aktivitas/respon mahasiswa dapat dikatakan sangat baik. Hasil belajar uji coba I dan uji coba II pada rumus t (test) pada skor 4,5 dan dapat dikatakan signifikan. Dari uraian diatas, dapat disimpulkan bahwa modul tata bahasa Indonesia tersebut layak digunakan
Kata Kunci: modul, tata bahasa, e-learning
Effects of Single-site Anisotropy on Mixed Diamond Chains with Spins 1 and 1/2
Effects of single-site anisotropy on mixed diamond chains with spins 1 and
1/2 are investigated in the ground states and at finite temperatures. There are
phases where the ground state is a spin cluster solid, i.e., an array of
uncorrelated spin-1 clusters separated by singlet dimers. The ground state is
nonmagnetic for the easy-plane anisotropy, while it is paramagnetic for the
easy-axis anisotropy. Also, there are the N\'eel, Haldane, and large-
phases, where the ground state is a single spin cluster of infinite size and
the system is equivalent to the spin-1 Heisenberg chain with alternating
anisotropy. The longitudinal and transverse susceptibilities and entropy are
calculated at finite temperatures in the spin-cluster-solid phases. Their
low-temperature behaviors are sensitive to anisotropy.Comment: 8 pages, 4 figure
Magnetization Plateaus in One Dimensional Heisenberg Model with Dimerization and Quadrumerization
The one dimensional Heisenberg model with dimerization () and
quadrumerization () in the magnetic field is studied by means of the
numerical exact diagonalization of finite size systems and the conformal field
theory. It is found that the magnetization plateau at half of the saturation
value exists for . For , this model is described by
the conformal field theory with central charge at this value of
magnetization. The critical exponent which characterizes the
-dependence of the width of the plateau is calculated using the level
spectroscopy method. The -dependence of the critical exponent is found
to be non-monotonic and discontinuous at . The effective theory of the
magnetization plateau is also presented for various limiting cases.Comment: 5 pages, 9 figure
Quasiperiodic Hubbard chains
Low energy properties of half-filled Fibonacci Hubbard models are studied by
weak coupling renormalization group and density matrix renormalization group
method. In the case of diagonal modulation, weak Coulomb repulsion is
irrelevant and the system behaves as a free Fibonacci chain, while for strong
Coulomb repulsion, the charge sector is a Mott insulator and the spin sector
behaves as a uniform Heisenberg antiferromagnetic chain. The off-diagonal
modulation always drives the charge sector to a Mott insulator and the spin
sector to a Fibonacci antiferromagnetic Heisenberg chain.Comment: 4 pages, 4 figures; Final version to appear in Phys. Rev. Let
Density Matrix Renormalization Group Study of the Haldane Phase in Random One-Dimensional Antiferromagnets
It is conjectured that the Haldane phase of the S=1 antiferromagnetic
Heisenberg chain and the ferromagnetic-antiferromagnetic alternating
Heisenberg chain is stable against any strength of randomness, because of
imposed breakdown of translational symmetry. This conjecture is confirmed by
the density matrix renormalization group calculation of the string order
parameter and the energy gap distribution.Comment: 4 Pages, 7 figures; Considerable revisions are made in abstract and
main text. Final accepted versio
Interacting Boson Theory of the Magnetization Process of the Spin-1/2 Ferromagnetic-Antiferromagnetic Alternating Heisenberg Chain
The low temperature magnetization process of the
ferromagnetic-antiferromagnetic Heisenberg chain is studied using the
interacting boson approximation. In the low field regime and near the
saturation field, the spin wave excitations are approximated by the
function boson gas for which the Bethe ansatz solution is available. The finite
temperature properties are calculated by solving the integral equation
numerically. The comparison is made with Monte Carlo calculation and the limit
of the applicability of the present approximation is discussed.Comment: 4 pages, 7 figure
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