514 research outputs found
Solitonic excitations in the Haldane phase of a S=1 chain
We study low-lying excitations in the 1D antiferromagnetic
valence-bond-solid (VBS) model. In a numerical calculation on finite systems
the lowest excitations are found to form a discrete triplet branch, separated
from the higher-lying continuum. The dispersion of these triplet excitations
can be satisfactorily reproduced by assuming approximate wave functions. These
wave functions are shown to correspond to moving hidden domain walls, i.e. to
one-soliton excitations.Comment: RevTex 3.0, 24 pages, 2 figures on request by fax or mai
Spectra of Heavy Quarkonia in a Magnetized-Hot Medium in the Framework of Fractional Non-relativistic Quark Model
In the fractional nonrelativistic potential model, the decomposition of heavy
quarkonium in a hot magnetized medium is investigated. The analytical solution
of the fractional radial Schrodinger equation for the hot-magnetized
interaction potential is displayed by using the conformable fractional
Nikiforov-Uvarov method. Analytical expressions for the energy eigenvalues and
the radial wave function are obtained for arbitrary quantum numbers. Next, we
study the charmonium and bottmonium binding energies for different magnetic
field values in the thermal medium. The effect of the fractional parameter on
the decomposition temperature is also analyzed for charmonium and bottomonium
in the presence of hot magnetized media. We conclude that the dissociation of
heavy quarkonium in the fractional nonrelativistic potential model is more
practical than the classical nonrelativistic potential model.Comment: 13 pages, 4 figures. arXiv admin note: substantial text overlap with
arXiv:2104.0054
Universality class of S=1/2 quantum spin ladder system with the four spin exchange
We study s=1/2 Heisenberg spin ladder with the four spin exchange. Combining
numerical results with the conformal field theory(CFT), we find a phase
transition with central charge c=3/2. Since this system has an SU(2) symmetry,
we can conclude that this critical theory is described by k=2 SU(2)
Wess-Zumino-Witten model with Z symmetry breaking
On the 3-particle scattering continuum in quasi one dimensional integer spin Heisenberg magnets
We analyse the three-particle scattering continuum in quasi one dimensional
integer spin Heisenberg antiferromagnets within a low-energy effective field
theory framework. We exactly determine the zero temperature dynamical structure
factor in the O(3) nonlinear sigma model and in Tsvelik's Majorana fermion
theory. We study the effects of interchain coupling in a Random Phase
Approximation. We discuss the application of our results to recent
neutron-scattering experiments on the Haldane-gap material .Comment: 8 pages of revtex, 5 figures, small changes, to appear in PR
A Brief History of AGN
Astronomers knew early in the twentieth century that some galaxies have
emission-line nuclei. However, even the systematic study by Seyfert (1943) was
not enough to launch active galactic nuclei (AGN) as a major topic of
astronomy. The advances in radio astronomy in the 1950s revealed a new universe
of energetic phenomena, and inevitably led to the discovery of quasars. These
discoveries demanded the attention of observers and theorists, and AGN have
been a subject of intense effort ever since. Only a year after the recognition
of the redshifts of 3C 273 and 3C 48 in 1963, the idea of energy production by
accretion onto a black hole was advanced. However, acceptance of this idea came
slowly, encouraged by the discovery of black hole X-ray sources in our Galaxy
and, more recently, supermassive black holes in the center of the Milky Way and
other galaxies. Many questions remain as to the formation and fueling of the
hole, the geometry of the central regions, the detailed emission mechanisms,
the production of jets, and other aspects. The study of AGN will remain a
vigorous part of astronomy for the foreseeable future.Comment: 37 pages, no figures. Uses aaspp4.sty. To be published in
Publications of the Astronomical Society of the Pacific, 1999 Jun
Staggered dimer order in S=1/2 quantum spin ladder system with four spin exchange
We study the S=1/2 quantum spin ladder system with the four-spin exchange,
using density matrix renormalization group method and an exact diagonalization
method. Recently, the phase transition in this system and its universality
class are studied. But there remain controversies whether the phase transition
is second order type or the other type and the nature of order parameter. There
are arguments that the massless phase appears. But this does not agree with our
previous result. Analyzing DMRG data, we try a new approach in order to
determine a phase which appears after the phase transition. We find that the
edge state appears in the open boundary condition, investigating excitation
energies of states with higher magnetizations.Comment: Submitted to Phys. Rev. B, (REVTeX4
Ambipolar gate effect and low temperature magnetoresistance of ultrathin La0.8Ca0.2MnO3 Films
Ultrathin La0.8Ca0.2MnO3 films have been measured in a field-effect geometry.
The electric field due to the gate produces a large ambipolar decrease in
resistance at low temperatures. This is attributed to the development of a
pseudogap in the density of states and the couple of localized charge to
strain. The gate effect and mangetoresistance are interpreted in a consistent
framework. The implications for the low temperature behavior of a manganite
film in the two dimensional limit are discussed.Comment: 4 pages, 3 figure
Maintenance therapy of patients with recurrent epithelial ovarian carcinoma with the anti-tumor-associated-mucin-1 antibody gatipotuzumab: results from a double-blind, placebo-controlled, randomized, phase II study
BACKGROUND: Gatipotuzumab is a humanized monoclonal antibody recognizing the carbohydrate-induced epitope of the tumor-associated mucin-1 (TA-MUC1). This study aimed to evaluate the efficacy and safety of switch maintenance therapy with gatipotuzumab in patients with TA-MUC1-positive recurrent ovarian, fallopian tube, or primary high-grade serous peritoneal cancer. PATIENTS AND METHODS: In this double-blind, randomized, placebo-controlled, phase II trial, patients with at least stable disease (SD) following chemotherapy were randomized 2:1 to receive intravenous gatipotuzumab (500 mg followed by 1700 mg 1 week later) or placebo every 3 weeks until tumor progression or unacceptable toxicity occurred. Stratification factors were the number of prior chemotherapy lines (2 versus 3-5), response versus SD after the most recent chemotherapy, and progression-free survival (PFS) <6 versus 6-12 months following the prior therapy. Primary endpoint was PFS according to modified immune-related RECIST 1.1 response criteria. Secondary endpoints were PFS at 6 months, safety, overall response rate, CA-125 progression, overall survival, quality of life, and pharmacokinetics. RESULTS: Overall, 216 patients were randomized to gatipotuzumab (n  =  151) or placebo (n  =  65). Median PFS with gatipotuzumab was 3.5 months as compared with 3.5 months with placebo (hazard ratio 0.96, 95% confidence interval 0.69-1.33, P  =  0.80). No advantage for gatipotuzumab over placebo was seen in the secondary efficacy endpoints or in any stratified subgroups. Gatipotuzumab was well tolerated, with mild to moderate infusion-related reactions being the most common adverse events. CONCLUSIONS: Gatipotuzumab switch maintenance therapy does not improve outcome in TA-MUC1-positive ovarian cancer patients. TRIAL REGISTRATION: ClinicalTrials.govNCT01899599; https://clinicaltrials.gov/ct2/show/NCT01899599
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