6,597 research outputs found
Where is the pseudoscalar glueball ?
The pseudoscalar mesons with the masses higher than 1 GeV are assumed to
belong to the meson decuplet including the glueball as the basis state
supplementing the standard nonet of light states
. The decuplet is investigated by means of an algebraic approach based
on hypothesis of vanishing the exotic commutators of "charges" and
their time derivatives. These commutators result in a system of equations
determining contents of the isoscalar octet state in the physical isoscalar
mesons as well as the mass formula including all masses of the decuplet:
, K(1460), , and . The physical
isoscalar mesons , are expressed as superpositions of the "ideal"
states ( and ) and the glueball with the mixing
coefficient matrix following from the exotic commutator restrictions. Among
four one-parameter families of the calculated mixing matrix (numerous solutions
result from bad quality of data on the and K(1460) masses) there is
one family attributing the glueball-dominant composition to the
meson. Similarity between the pseudoscalar and scalar decuplets, analogy
between the whole spectra of the and mesons and affinity of
the glueball with excited states are also noticed.Comment: 18 pp., 2. figs., 2 tabs.; Published version. One of the authors
withdraws his nam
Ergodic property of Markovian semigroups on standard forms of von Neumann algebras
We give sufficient conditions for ergodicity of the Markovian semigroups
associated to Dirichlet forms on standard forms of von Neumann algebras
constructed by the method proposed in Refs. [Par1,Par2]. We apply our result to
show that the diffusion type Markovian semigroups for quantum spin systems are
ergodic in the region of high temperatures where the uniqueness of the
KMS-state holds.Comment: 25 page
Design and Evaluation of Heterobivalent PAR1–PAR2 Ligands as Antagonists of Calcium Mobilization
A novel class of bivalent ligands targeting putative protease-activated receptor (PAR) heteromers has been prepared based upon reported antagonists for the subtypes PAR1 and PAR2. Modified versions of the PAR1 antagonist RWJ-58259 containing alkyne adapters were connected via cycloaddition reactions to azide-capped polyethylene glycol (PEG) spacers attached to imidazopyridazine-based PAR2 antagonists. Initial studies of the PAR1–PAR2 antagonists indicated that they inhibited G alpha q-mediated calcium mobilization in endothelial and cancer cells driven by both PAR1 and PAR2 agonists. Compounds of this novel class hold promise for the prevention of restenosis, cancer cell metastasis, and other proliferative disorders
A patient with abnormalities of the coronary arteries and non-compaction of the left ventricular myocardium resulting in ischaemic heart disease symptoms
Left ventricular non-compaction (LVNC) is a rare cardiomyopathy that results from unsettled embryogenesis of myocardium. It is morphologically characterised by the presence of non-compacted, this is hypertrabeculated, myocardium of the left ventricle with deep endocardial recesses. The clinical spectrum of symptoms is very wide — from asymptomatic patients through the cases of heart failure to the patients requiring heart transplantation. The diagnosis is most frequently based on the echocardiography. LVNC is often coexisted with other heart defects and coronary artery abnormalities. We described a case of a 58-year-old man with LVNC and coronary artery anomalies
On non-completely positive quantum dynamical maps on spin chains
The new arguments based on Majorana fermions indicating that non-completely
positive maps can describe open quantum evolution are presented.Comment: published; small change
Epitaxial growth and magnetic properties of Sr2CrReO6 thin films
The double perovskite Sr2CrReO6 is an interesting material for spintronics,
showing ferrimagnetism up to 635 K with a predicted high spin polarization of
about 86%. We fabricated Sr2CrReO6 epitaxial films by pulsed laser deposition
on (001)-oriented SrTiO3 substrates. Phase-pure films with optimum
crystallographic and magnetic properties were obtained by growing at a
substrate temperature of 700 degree C in pure O2 of 6.6x10-4 mbar. The films
are c-axis oriented, coherently strained, and show less than 20% anti-site
defects. The magnetization curves reveal high saturation magnetization of 0.8
muB per formula unit and high coercivity of 1.1 T, as well as a strong magnetic
anisotropy.Comment: accepted for publicatio
Radon-Nikodym derivatives of quantum operations
Given a completely positive (CP) map , there is a theorem of the
Radon-Nikodym type [W.B. Arveson, Acta Math. {\bf 123}, 141 (1969); V.P.
Belavkin and P. Staszewski, Rep. Math. Phys. {\bf 24}, 49 (1986)] that
completely characterizes all CP maps such that is also a CP map. This
theorem is reviewed, and several alternative formulations are given along the
way. We then use the Radon-Nikodym formalism to study the structure of order
intervals of quantum operations, as well as a certain one-to-one correspondence
between CP maps and positive operators, already fruitfully exploited in many
quantum information-theoretic treatments. We also comment on how the
Radon-Nikodym theorem can be used to derive norm estimates for differences of
CP maps in general, and of quantum operations in particular.Comment: 22 pages; final versio
Constraining the History of the Sagittarius Dwarf Galaxy Using Observations of its Tidal Debris
We present a comparison of semi-analytic models of the phase-space structure
of tidal debris with observations of stars associated with the Sagittarius
dwarf galaxy (Sgr). We find that many features in the data can be explained by
these models. The properties of stars 10-15 degrees away from the center of Sgr
--- in particular, the orientation of material perpendicular to Sgr's orbit
(c.f. Alard 1996) and the kink in the velocity gradient (Ibata et al 1997) ---
are consistent with those expected for unbound material stripped during the
most recent pericentric passage ~50 Myrs ago. The break in the slope of the
surface density seen by Mateo, Olszewski & Morrison (1998) at ~ b=-35 can be
understood as marking the end of this material. However, the detections beyond
this point are unlikely to represent debris in a trailing streamer, torn from
Sgr during the immediately preceding passage ~0.7 Gyrs ago, but are more
plausibly explained by a leading streamer of material that was lost more that 1
Gyr ago and has wrapped all the way around the Galaxy. The observations
reported in Majewski et al (1999) also support this hypothesis. We determine
debris models with these properties on orbits that are consistent with the
currently known positions and velocities of Sgr in Galactic potentials with
halo components that have circular velocities v_circ=140-200 km/s. The best
match to the data is obtained in models where Sgr currently has a mass of ~10^9
M_sun and has orbited the Galaxy for at least the last 1 Gyr, during which time
it has reduced its mass by a factor of 2-3, or luminosity by an amount
equivalent to ~10% of the total luminosity of the Galactic halo. These numbers
suggest that Sgr is rapidly disrupting and unlikely to survive beyond a few
more pericentric passages.Comment: 19 pages, 5 figures, accepted to Astronomical Journa
Spectroscopy of Giant Stars in the Pyxis Globular Cluster
The Pyxis globular cluster is a recently discovered globular cluster that
lies in the outer halo (R_{gc} ~ 40 kpc) of the Milky Way. Pyxis lies along one
of the proposed orbital planes of the Large Magellanic Cloud (LMC), and it has
been proposed to be a detached LMC globular cluster captured by the Milky Way.
We present the first measurement of the radial velocity of the Pyxis globular
cluster based on spectra of six Pyxis giant stars. The mean heliocentric radial
velocity is ~ 36 km/sec, and the corresponding velocity of Pyxis with respect
to a stationary observer at the position of the Sun is ~ -191 km/sec. This
radial velocity is a large enough fraction of the cluster's expected total
space velocity, assuming that it is bound to the Milky Way, that it allows
strict limits to be placed on the range of permissible transverse velocities
that Pyxis could have in the case that it still shares or nearly shares an
orbital pole with the LMC. We can rule out that Pyxis is on a near circular
orbit if it is Magellanic debris, but we cannot rule out an eccentric orbit
associated with the LMC. We have calculated the range of allowed proper motions
for the Pyxis globular cluster that result in the cluster having an orbital
pole within 15 degrees of the present orbital pole of the LMC and that are
consistent with our measured radial velocity, but verification of the tidal
capture hypothesis must await proper motion measurement from the Space
Interferometry Mission or HST. A spectroscopic metallicity estimate of [Fe/H] =
-1.4 +/- 0.1 is determined for Pyxis from several spectra of its brightest
giant; this is consistent with photometric determinations of the cluster
metallicity from isochrone fitting.Comment: 22 pages, 5 figures, aaspp4 style, accepted for publication in
October, 2000 issue of the PAS
- …