3,878 research outputs found
A new description of motion of the Fermionic SO(2N+2) top in the classical limit under the quasi-anticommutation relation approximation
The boson images of fermion SO(2N+1) Lie operators have been given together
with those of SO(2N+2) ones. The SO(2N+1) Lie operators are generators of
rotation in the (2N+1)-dimensional Euclidian space (N: number of
single-particle states of the fermions). The images of fermion
annihilation-creation operators must satisfy the canonical anti-commutation
relations, when they operate on a spinor subspace. In the regular
representation space we use a boson Hamiltonian with Lagrange multipliers to
select out the spinor subspace. Based on these facts, a new description of a
fermionic SO(2N+2) top is proposed. From the Heisenberg equations of motions
for the boson operators, we get the SO(2N+1) self-consistent field (SCF)
Hartree-Bogoliubov (HB) equation for the classical stationary motion of the
fermion top. Decomposing an SO(2N+1) matrix into matrices describing paired and
unpaired modes of fermions, we obtain a new form of the SO(2N+1) SCF equation
with respect to the paired-mode amplitudes. To demonstrate the effectiveness of
the new description based on the bosonization theory, the extended HB
eigenvalue equation is applied to a superconducting toy-model which consists of
a particle-hole plus BCS type interaction. It is solved to reach an interesting
and exciting solution which is not found in the traditional HB eigenvalue
equation, due to the unpaired-mode effects. To complete the new description,
the Lagrange multipliers must be determined in the classical limit. For this
aim a quasi anti-commutation-relation approximation is proposed. Only if a
certain relation between an SO(2N+1) parameter z and the N is satisfied,
unknown parameters k and l in the Lagrange multipliers can be determined
withuout any inconcistency.Comment: 36 pages, no figures, typos corrected, published versio
Can the frequency-dependent specific heat be measured by thermal effusion methods?
It has recently been shown that plane-plate heat effusion methods devised for
wide-frequency specific-heat spectroscopy do not give the isobaric specific
heat, but rather the so-called longitudinal specific heat. Here it is shown
that heat effusion in a spherical symmetric geometry also involves the
longitudinal specific heat.Comment: Paper presented at the Fifth International Workshop on Complex
Systems (Sendai, September, 2007), to appear in AIP Conference Proceeding
Large scale kinematics and dynamical modelling of the Milky Way nuclear star cluster
Within the central 10pc of our Galaxy lies a dense nuclear star cluster
(NSC), and similar NSCs are found in most nearby galaxies. Studying the
structure and kinematics of NSCs reveals the history of mass accretion of
galaxy nuclei. Because the Milky Way (MW) NSC is at a distance of only 8kpc, we
can spatially resolve the MWNSC on sub-pc scales. This makes the MWNSC a
reference object for understanding the formation of all NSCs. We have used the
NIR long-slit spectrograph ISAAC (VLT) in a drift-scan to construct an
integral-field spectroscopic map of the central 9.5 x 8pc of our Galaxy. We use
this data set to extract stellar kinematics both of individual stars and from
the unresolved integrated light spectrum. We present a velocity and dispersion
map from the integrated light and model these kinematics using kinemetry and
axisymmetric Jeans models. We also measure CO bandhead strengths of 1,375
spectra from individual stars. We find kinematic complexity in the NSCs radial
velocity map including a misalignment of the kinematic position angle by 9
degree counterclockwise relative to the Galactic plane, and indications for a
rotating substructure perpendicular to the Galactic plane at a radius of 20" or
0.8pc. We determine the mass of the NSC within r = 4.2pc to 1.4 x 10^7 Msun. We
also show that our kinematic data results in a significant underestimation of
the supermassive black hole (SMBH) mass. The kinematic substructure and
position angle misalignment may hint at distinct accretion events. This
indicates that the MWNSC grew at least partly by the mergers of massive star
clusters. Compared to other NSCs, the MWNSC is on the compact side of the r_eff
- M_NSC relation. The underestimation of the SMBH mass might be caused by the
kinematic misalignment and a stellar population gradient. But it is also
possible that there is a bias in SMBH mass measurements obtained with
integrated light.Comment: 20 pages, 19 Figures, Accepted for publication in A&
High resolution observations of Cen A: Yellow and red supergiants in a region of jet-induced star formation?
We present the analysis of near infrared (NIR), adaptive optics (AO) Subaru
and archived HST imaging data of a region near the northern middle lobe (NML)
of the Centaurus A (Cen A) jet, at a distance of kpc north-east (NE)
from the center of NGC5128. Low-pass filtering of the NIR images reveals strong
-- above the background mean -- signal at the expected position of
the brightest star in the equivalent HST field. Statistical analysis of the NIR
background noise suggests that the probability to observe signal at
the same position, in three independent measurements due to stochastic
background fluctuations alone is negligible () and, therefore,
that this signal should reflect the detection of the NIR counterparts of the
brightest HST star. An extensive photometric analysis of this star yields
, visual-NIR, and NIR colors expected from a yellow supergiant (YSG) with
an estimated age Myr. Furthermore, the second and third
brighter HST stars are, likely, also supergiants in Cen A, with estimated ages
Myr and Myr, respectively. The ages of
these three supergiants are in good agreement with the ages of the young
massive stars that were previously found in the vicinity and are thought to
have formed during the later phases of the jet-HI cloud interaction that
appears to drive the star formation (SF) in the region for the past
Myr.Comment: 11 pages, 6 figures, 2 tables, accepted for publication in Ap
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