6,800 research outputs found
Nuclear G-Matrix Elements from Nonlocal Potentials
We study effects of nonlocality in the nuclear force on the G-matrix elements
for finite nuclei. Nuclear G-matrix elements for \O16 are calculated in the
harmonic oscillator basis from a nonlocal potential which models quark exchange
effects between two nucleons. We employ a simple form of potential that gives
the same phase shifts as a realistic local nucleon potential. The G-matrix
elements calculated from the nonlocal potential show moderate increase in
repulsion from those derived from the local potential.Comment: 11 page, LaTeX, 2 PS figures, uses epsf.st
Relation between the separable and one-boson-exchange potential for the covariant Bethe-Salpeter equation
We investigate the relation between the rank I separable potential for the
covariant Bethe-Salpeter equation and the one-boson-exchange potential. After
several trials of the parameter choices, it turns out that it is not always
possible to reproduce the phase-shifts calculated from a single term of the
one-boson-exchange potential especially of the -exchange term,
separately by the rank I separable potential. Instead, it is shown that the
separable potential is useful to parameterize the total nucleon-nucleon
interaction.Comment: 10 pages, 8 figures, to appear in J.Phys.
Quantum description for a chiral condensate disoriented in a certain direction in isospace
We derive a quantum state of the disoriented chiral condensate dynamically,
considering small quantum fluctuations around a classical chiral condensate
disoriented in a certain direction in isospace. The obtained
nonisosinglet quantum state has the characteristic features; (i) it has the
form of the squeezed state, (ii) the state contains not only the component of
pion quanta in the direction but also the component in the
perpendicular direction to and (iii) the low momentum pions in the
state violate the isospin symmetry. With the quantum state, we calculate the
probability of the neutral fraction depending on the time and the pion's
momentum, and find that the probability has an unfamiliar form. For the low
momentum pions, the parametric resonance mechanism works with the result that
the probability of the neutral fraction becomes the well known form
approximately and that the charge fluctuation is small.Comment: 19 page
Absorption Line Survey of H3+ toward the Galactic Center Sources III. Extent of the Warm and Diffuse Clouds
We present follow-up observations to those of Geballe & Oka (2010), who found
high column densities of H3+ ~100 pc off of the Galactic center (GC) on the
lines of sight to 2MASS J17432173-2951430 (J1743) and 2MASS J17470898-2829561
(J1747). The wavelength coverages on these sightlines have been extended in
order to observe two key transitions of H3+, R(3,3)l and R(2,2)l, that
constrain the temperatures and densities of the environments. The profiles of
the H3+ R(3,3)l line, which is due only to gas in the GC, closely matches the
differences between the H3+ R(1,1)l and CO line profiles, just as it does for
previously studied sightlines in the GC. Absorption in the R(2,2)l line of H3+
is present in J1747 at velocities between -60 and +100 km/s. This is the second
clear detection of this line in the interstellar medium after GCIRS 3 in the
Central Cluster. The temperature of the absorbing gas in this velocity range is
350 K, significantly warmer than in the diffuse clouds in other parts of the
Central Molecular Zone. This indicates that the absorbing gas is local to Sgr B
molecular cloud complex. The warm and diffuse gas revealed by Oka et al. (2005)
apparently extends to ~100 pc, but there is a hint that its temperature is
somewhat lower in the line of sight to J1743 than elsewhere in the GC. The
observation of H3+ toward J1747 is compared with the recent Herschel
observation of H2O+ toward Sgr B2 and their chemical relationship and
remarkably similar velocity profiles are discussed.Comment: 6 pages, 3 figures, 2 tables, Accepted for publication in
Publications of the Astronomical Society of Japa
Evaluasi Modulasi MFSK Untuk Transmisi Data Melalui Kanal Suara GSM
Pada tulisan ini, dievaluasi performansi skema modulasi MFSK (M-ary Frequency Shift Keying) untuk aplikasi pengiriman data melalui kanal suara GSM (Global System for Mobile Communication). Parameter yang dievaluasi berupa kesalahan bit trasmisi yang dinyatakan dengan laju kesalahan bit atau bit error rate (BER). Evaluasi ini dilakukan untuk menentukan besarnya orde M yang akan dipilih pada aplikasi pengiriman data digital melalui kanal suara GSM. Pada proses simulasi, data digital dikodekan menjadi simbol-simbol lalu dimodulasi menggunakan modulator MFSK menjadi data menyerupai pembicaraan (suara). Suara yang dihasilkan dikodekan dengan algoritma CELP (Code Excited Linear Prediction), kemudian dikirimkan melalui udara yang dimodelkan sebagai kanal AWGN (Additive White Gaussian Noise). Di sisi penerima, sinyal terima yang menyerupai suara ini didemodulasi dan dikonversi kembali menjadi data digital. Dari simulasi menggunakan Eb/No (signal to noise ratio) sebesar 6 dB, diperoleh laju bit 2,5 kbps dengan BER 2,01 x 10-3 untuk M=4, 2,22 x 10-3 untuk M=8, dan 1,87 x 10-3 untuk M=16
Ground-State Decay Rate for the Zener Breakdown in Band and Mott Insulators
Non-linear transport of electrons in strong electric fields, as typified by
dielectric breakdown, is re-formulated in terms of the ground-state decay rate
originally studied by Schwinger in non-linear QED. We discuss the effect of
electron interaction on Zener tunneling by comparing the dielectric breakdown
of the band insulator and the Mott insulator, where the latter is studied by
the time-dependent density-matrix renormalization group (DMRG). The relation
with the Berry's phase theory of polarization is also established.Comment: 5 pages 2 figures, revised text, version to appear in Phys. Rev. Let
The Interstellar Medium of IRAS 08572+3915 NW: H3+ and Warm High Velocity CO
We confirm the first detection of the molecular ion H3+ in an extragalactic
object, the highly obscured ultraluminous galaxy IRAS 08572+3915 NW. We also
have detected absorption lines of the fundamental band of CO in this galaxy.
The CO absorption consists of a cold component close to the systemic velocity
and warm, highly blueshifted and redshifted components. The warm blueshifted
component is remarkably strong and broad and extends at least to -350 km/s.
Some analogies can be drawn between the H3+ and cold CO in IRAS08572+3915 NW
and the same species seen toward the Galactic center. The profiles of the warm
CO components are not those expected from a dusty torus of the type thought to
obscure active galactic nuclei. They are probably formed close to the dust
continuum surface near the buried and active nucleus and are probably
associated with an unusual and energetic event there.Comment: 21 pages, 4 postscript figures, accepted by Ap
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