10,636 research outputs found
A method to study complex systems of mesons in Lattice QCD
Finite density systems can be explored with Lattice QCD through the
calculation of multi-hadron correlation functions. Recently, systems with up to
12 's or 's have been studied to determine the 3- and
3- interactions, and the corresponding chemical potentials have been
determined as a function of density. We derive recursion relations between
correlation functions that allow this work to be extended to systems of
arbitrary numbers of mesons and to systems containing many different types of
mesons, such as 's, 's, 's and 's. These relations
allow for the study of finite-density systems in arbitrary volumes, and for the
study of high-density systems.Comment: JLAB-THY-10-1121, NT@UW-10-01, journal versio
Characterizing Transition Temperature Gas in the Galactic Corona
We present a study of the properties of the transition temperature (T~10^5 K)
gas in the Milky Way corona, based on measurements of OVI, NV, CIV, SiIV and
FeIII absorption lines seen in the far ultraviolet spectra of 58 sightlines to
extragalactic targets, obtained with Far-Ultraviolet Spectroscopic Explorer
(FUSE) and Space Telescope Imaging Spectrograph. In many sightlines the
Galactic absorption profiles show multiple components, which are analyzed
separately. We find that the highly-ionized atoms are distributed irregularly
in a layer with a scaleheight of about 3 kpc, which rotates along with the gas
in the disk, without an obvious gradient in the rotation velocity away from the
Galactic plane. Within this layer the gas has randomly oriented velocities with
a dispersion of 40-60 km/s. On average the integrated column densities are log
N(OVI)=14.3, log N(NV)=13.5, log N(CIV)=14.2, log N(SiIV)=13.6 and log
N(FeIII)=14.2, with a dispersion of just 0.2 dex in each case. In sightlines
around the Galactic Center and Galactic North Pole all column densities are
enhanced by a factor ~2, while at intermediate latitudes in the southern sky
there is a deficit in N(OVI) of about a factor 2, but no deficit for the other
ions. We compare the column densities and ionic ratios to a series of
theoretical predictions: collisional ionization equilibrium, shock ionization,
conductive interfaces, turbulent mixing, thick disk supernovae, static
non-equilibrium ionization (NIE) radiative cooling and an NIE radiative cooling
model in which the gas flows through the cooling zone. None of these models can
fully reproduce the data, but it is clear that non-equilibrium ionization
radiative cooling is important in generating the transition temperature gas.Comment: 99 pages, 11 figures, with appendix on Cooling Flow model; only a
sample of 5 subfigures of figure 2 included - full set of 69 available
through Ap
Fundamental Properties of the Highly Ionized Plasmas in the Milky Way
The cooling transition temperature gas in the interstellar medium (ISM),
traced by the high ions, Si IV, C IV, N V, and O VI, helps to constrain the
flow of energy from the hot ISM with T >10^6 K to the warm ISM with T< 2x10^4
K. We investigate the properties of this gas along the lines of sight to 38
stars in the Milky Way disk using 1.5-2.7 km/s resolution spectra of Si IV, C
IV, and N V absorption from the Space Telescope Imaging Spectrograph (STIS),
and 15 km/s resolution spectra of O VI absorption from the Far Ultraviolet
Spectroscopic Explorer (FUSE). The absorption by Si IV and C IV exhibits broad
and narrow components while only broad components are seen in N V and O VI. The
narrow components imply gas with T<7x10^4 K and trace two distinct types of
gas. The strong, saturated, and narrow Si IV and C IV components trace the gas
associated with the vicinities of O-type stars and their supershells. The
weaker narrow Si IV and C IV components trace gas in the general ISM that is
photoionized by the EUV radiation from cooling hot gas or has radiatively
cooled in a non-equilibrium manner from the transition temperature phase, but
rarely the warm ionized medium (WIM) probed by Al III. The broad Si IV, C IV, N
V, and O VI components trace collisionally ionized gas that is very likely
undergoing a cooling transition from the hot ISM to the warm ISM. The cooling
process possibly provides the regulation mechanism that produces N(C IV)/N(Si
IV) = 3.9 +/- 1.9. The cooling process also produces absorption lines where the
median and mean values of the line widths increase with the energy required to
create the ion.Comment: Accepted for publication in the ApJ. Only this PDF file contains all
the figures and tables in a single fil
GHRS and ORFEUS-II Observations of the Highly Ionized Interstellar Medium Toward ESO141-055
We present Goddard High Resolution Spectrograph and ORFEUS-II measurements of
Si IV, CIV, N V, and O VI absorption in the interstellar medium of the Galactic
disk and halo toward the nucleus of the Seyfert galaxy ESO141-055. The high
ionization absorption is strong, with line strengths consistent with the
spectral signature expected for hot (log T = 5-6) collisionally ionized gas in
either a ``Galactic fountain'' or an inhomogeneous medium containing a mixture
of conductive interfaces and turbulent mixing layers. The total O VI column
density of log N ~ 15 suggests that the scale height of O VI is large (>3 kpc)
in this direction. Comparison of the high ion column densities with
measurements for other sight lines indicates that the highly ionized gas
distribution is patchy. The amount of O VI perpendicular to the Galactic plane
varies by at least a factor of ~4 among the complete halo sight lines thus far
studied. In addition to the high ion absorption, lines of low ionization
species are also present in the spectra. With the possible exception of Ar I,
which may have a lower than expected abundance resulting from partial
photoionization of gas along the sight line, the absorption strengths are
typical of those expected for the warm, neutral interstellar medium. The sight
line intercepts a cold molecular cloud with log N(H2) ~ 19. The cloud has an
identifiable counterpart in IRAS 100-micron emission maps of this region of the
sky. We detect a Ly-alpha absorber associated with ESO141-055 at z = 0.03492.
This study presents an enticing glimpse into the interstellar and intergalactic
absorption patterns that will be observed at high spectral resolution by the
Far Ultraviolet Spectroscopic Explorer.Comment: 24 pages + 8 figures, uses aaspp4.sty. Accepted for publication in
Ap
BB Potentials in Quenched Lattice QCD
The potentials between two B-mesons are computed in the heavy-quark limit
using quenched lattice QCD at . Non-zero central
potentials are clearly evident in all four spin-isospin channels, (I,s_l) =
(0,0) , (0,1) , (1,0) , (1,1), where s_l is the total spin of the light degrees
of freedom. At short distance, we find repulsion in the channels and
attraction in the I=s_l channels. Linear combinations of these potentials that
have well-defined spin and isospin in the t-channel are found, in three of the
four cases, to have substantially smaller uncertainties than the potentials
defined with the s-channel (I,s_l), and allow quenching artifacts from single
hairpin exchange to be isolated. The BB*\pi coupling extracted from the
long-distance behavior of the finite-volume t-channel potential is found to be
consistent with quenched calculations of the matrix element of the isovector
axial-current. The tensor potentials in both of the s_l = 1 channels are found
to be consistent with zero within calculational uncertainties.Comment: 30 page
Decay of Hypernuclei
We present a nonrelativistic transition potential for the weak
strangeness-changing reaction . The potential is based on a
one meson exchange model (OME), where, in addition to the long-ranged pion, the
exchange of the pseudoscalar , as well as the vector mesons is considered. Results obtained for different hypernuclear decay
observables are compared to the available experimental data.Comment: 8 pages. Invited talk given at the KEK-Tanashi International
Symposium on Physics of Hadrons and Nuclei. Tokyo, Japan, December 14-17,
1998. In honor of Prof. K. Yazaki. Submitted to Nucl. Phys. A. LateX file
(uses espcrc1.sty
Pathobiology of nodal peripheral T-cell lymphomas: current understanding and future directions.
Predominantly nodal is the most common clinical presentation of peripheral T- (and NK-) cell lymphomas (PTCL), which comprise three main groups of diseases: (i) systemic anaplastic large cell lymphomas (ALCL), whether positive or negative for anaplastic lymphoma kinase (ALK); (ii) follicular helper T-cell lymphomas (TFHL); and (iii) PTCL, not otherwise specified (NOS). Recent advances in the genomic and molecular characterization of PTCL, with enhanced understanding of pathobiology, have translated into significant updates in the latest 2022 classifications of lymphomas. ALK-negative ALCL is now recognized to be genetically heterogeneous, with identification of DUSP22 rearrangements in approximately 20-30% of cases, correlated with distinctive pathological and biological features. The notion of cell-of-origin as an important determinant of the classification of nodal PTCL is best exemplified by TFHL, considered as one disease or a group of related entities, sharing oncogenic pathways with frequent recurrent epigenetic mutations as well as a relationship to clonal hematopoiesis. Data are emerging to support that a similar cell-of-origin concept might be relevant to characterize meaningful subgroups within PTCL, NOS, based on cytotoxic and/or Th1 versus Th2 signatures. The small group of primary nodal Epstein-Barr virus-positive lymphomas of T- or NK-cell derivation, formerly considered PTCL, NOS, is now classified separately, due to distinctive features, and notably an aggressive course. This review summarizes current knowledge of the pathology and biology of nodal-based PTCL entities, with an emphasis on recent findings and underlying oncogenic mechanisms
Harmonic Text-Painting in Franz Liszt’s Lieder
Despite their effectiveness and general appeal, Liszt’s Lieder have not attracted the same level of interest among scholars and analysts as those of other first-rank composers of the nineteenth century. Liszt’s innovative approach to harmony, which includes a high degree of chromaticism and enharmonic shifts, along with frequent changes of tonal focus and tonal ambiguity, often frustrates efforts at analysis that attempt to reveal unified tonal structures. These factors have encouraged a view of this repertoire as uneven or inconsistent. In this study we explain Liszt’s distinctive approach to text setting as a dichotomy between traditional and progressive tonal-harmonic practices that parallels the contrasts between Classical and Romantic aesthetics and related ideas and images that operate within the poetry. We demonstrate, through the examination of surface-level harmonic progressions as well as large-scale tonal relationships, how Liszt’s Lieder reflect the conflicts and contradictions between these two sets of ideas, and the search for understanding or resolution. Analyses of individual songs illustrate both the richness and the consistency of Liszt’s harmonic style, in conveying and interpreting the meaning of texts dealing with common Romantic subjects
Extreme host galaxy growth in powerful early-epoch radio galaxies
During the first half of the universe's age, a heyday of star-formation must
have occurred because many massive galaxies are in place after that epoch in
cosmic history. Our observations with the revolutionary Herschel Space
Observatory reveal vigorous optically obscured star-formation in the
ultra-massive hosts of many powerful high-redshift 3C quasars and radio
galaxies. This symbiotic occurrence of star-formation and black hole driven
activity is in marked contrast to recent results dealing with Herschel
observations of X-ray selected active galaxies. Three archetypal radio
galaxies, at redshifts 1.132,1.575, and 2.474 are presented here, with inferred
star-formation rates of hundreds of solar masses per year. A series of
spectacular coeval AGN/starburst events may have formed these ultra-massive
galaxies and their massive central black holes during their relatively short
lifetimes.Comment: To appear in Astrophysical Journal Letter
- …