172 research outputs found
Skyrmions in quantum Hall ferromagnets as spin-waves bound to unbalanced magnetic flux quanta
A microscopic description of (baby)skyrmions in quantum Hall ferromagnets is
derived from a scattering theory of collective (neutral) spin modes by a bare
quasiparticle. We start by mapping the low lying spectrum of spin waves in the
uniform ferromagnet onto that of free moving spin excitons, and then we study
their scattering by the defect of charge. In the presence of this disturbance,
the local spin stiffness varies in space, and we translate it into an
inhomogeneus metric in the Hilbert space supporting the excitons. An attractive
potencial is then required to preserve the symmetry under global spin
rotations, and it traps the excitons around the charged defect. The
quasiparticle now carries a spin texture. Textures containing more than one
exciton are described within a mean-field theory, the interaction among the
excitons being taken into account through a new renormalization of the metric.
The number of excitons actually bound depends on the Zeeman coupling, that
plays the same role as a chemical potencial. For small Zeeman energies, the
defect binds many excitons which condensate. As the bound excitons have a unit
of angular momentum, provided by the quantum of magnetic flux left unbalanced
by the defect of charge, the resulting texture turns out to be a topological
excitation of charge 1. Its energy is that given by the non-linear sigma model
for the ground state in this topological sector, i.e. the texture is a
skyrmion.Comment: 17 pages, 1 figur
Broken Symmetries in the Reconstruction of v=1 Quantum Hall Edges
Spin-polarized reconstruction of the v=1 quantum Hall edge is accompanied by
a spatial modulation of the charge density along the edge. We find that this is
also the case for finite quantum Hall droplets: current spin density functional
calculations show that the so-called Chamon-Wen edge forms a ring of apparently
localized electrons around the maximum density droplet (MDD). The boundaries of
these different phases qualitatively agree with recent experiments. For very
soft confinement, Chern-Simons Ginzburg-Landau theory indicates formation of a
non-translational invariant edge with vortices (holes) trapped in the edge
region.Comment: Proceedings of the EP2DS, Ottawa (1999) (submitted to Physica E
Kondo effect in multielectron quantum dots at high magnetic fields
We present a general description of low temperature transport through a
quantum dot with any number of electrons at filling factor . We
provide a general description of a novel Kondo effect which is turned on by
application of an appropriate magnetic field. The spin-flip scattering of
carriers by the quantum dot only involves two states of the scatterer which may
have a large spin. This process is described by spin-flip Hubbard operators,
which change the angular momentum, leading to a Kondo Hamiltonian. We obtain
antiferromagnetic exchange couplings depending on tunneling amplitudes and
correlation effects. Since Kondo temperature has an exponential dependence on
exchange couplings, quantitative variations of the parameters in different
regimes have important experimental consequences. In particular, we discuss the
{\it chess board} aspect of the experimental conductance when represented in a
grey scale as a function of both the magnetic field and the gate potential
affecting the quantum dot
Spin-isospin textured excitations in a double layer at filling factor
We study the charged excitations of a double layer at filling factor 2 in the
ferromagnetic regime. In a wide range of Zeeman and tunneling splittings we
find that the low energy charged excitations are spin-isospin textures with the
charge mostly located in one of the layers. As tunneling increases, the parent
spin texture in one layer becomes larger and it induces, in the other layer, a
shadow spin texture antiferromagnetically coupled to the parent texture. These
new quasiparticles should be observable by measuring the strong dependence of
its spin on tunneling and Zeeman couplings.Comment: 4 pages, 4 figure
Edge Theories for Polarized Quantum Hall States
Starting from recently proposed bosonic mean field theories for fully and
partially polarized quantum Hall states, we construct corresponding effective
low energy theories for the edge modes. The requirements of gauge symmetry and
invariance under global O(3) spin rotations, broken only by a Zeeman coupling,
imply boundary conditions that allow for edge spin waves. In the generic case,
these modes are chiral, and the spin stiffness differs from that in the bulk.
For the case of a fully polarized state, our results agree with
previous Hartree-Fock calculations.Comment: 15 pages (number of pages has been reduced by typesetting in RevTeX);
2 references adde
Extended Friedberg Lee hidden symmetries, quark masses and CP-violation with four generations
Motivated in part by the several observed anomalies involving CP asymmetries
of B and B_s decays, we consider the Standard Model with a 4th sequential
family (SM4) which seems to offer a rather simple resolution. We initially
assume T-invariance by taking the up and down-quark 4x4 mass matrix to be real.
Following Friedberg and Lee (FL), we then impose a "hidden" symmetry on the
unobserved ("hidden") up and down-quark SU(2) states. The hidden symmetry for
four generations ensures the existence of two zero-mass eigenstates, which we
take to be the (u,c) and (d,s) states in the up and down-quark sectors,
respectively. Then, we simultaneously break T-invariance and the hidden
symmetry by introducing two phase factors in each sector. This breaking
mechanism generates the small quark masses m_u, m_c and m_d, m_s which, along
with the orientation of the hidden symmetry, determine the size of CP-violation
in the SM4. For illustration we choose a specific physical picture for the
hidden symmetry and the breaking mechanism that reproduces the observed quark
masses, mixing angles and CP-violation, and at the same time allows us to
further obtain very interesting relations/predictions for the mixing angles of
t and t'. For example, with this choice we get V_{td} ~ (V_{cb}/V_{cd} -
V_{ts}/V_{us}) + O(\lambda^2) and V_{t'b} ~ V_{t'd}x(V_{cb}/V_{cd}), V_{tb'} ~
V_{t'd}x(V_{ts}/V_{us}), implying that V_{t'd} > V_{t'b},V_{tb'}. We
furthermore find that the Cabibbo angle is related to the orientation of the
hidden symmetry and that the key CP-violating quantity of our model at
high-energies, J_{SM4} = Im[V_{tb} V_{t'b}^* V_{t'b'} V_{tb'}^*], which is the
high-energy analogue of the Jarlskog invariant of the SM, is proportional to
the light-quark masses and the measured CKM angles.Comment: 19 page
Pan-Asian adapted ESMO Clinical Practice Guidelines for the diagnosis, treatment and follow-up of patients with endometrial cancer
Endometrial cancer; Guidelines; TreatmentCà ncer d'endometri; Pautes; TractamentCáncer de endometrio; Pautas; TratamientoThe most recent version of the European Society for Medical Oncology (ESMO) Clinical Practice Guidelines for the diagnosis, treatment and follow-up of patients with endometrial cancer was published in 2022. It was therefore decided, by both the ESMO and the Indian Society of Medical and Paediatric Oncology (ISMPO), to convene a virtual meeting in July 2022 to adapt the ESMO 2022 guidelines to take into account the variations in the management of endometrial cancer in Asia. These guidelines represent the consensus opinion of a panel of Asian experts representing the oncological societies of China (CSCO), India (ISMPO), Indonesia (ISHMO), Japan (JSMO), Korea (KSMO), Malaysia (MOS), the Philippines (PSMO), Singapore (SSO), Taiwan (TOS) and Thailand (TSCO). Voting was based on scientific evidence and was conducted independently of the current treatment practices and treatment access constraints in the different Asian countries, which were discussed when appropriate. The aim of this guideline manuscript is to provide guidance for the optimisation and harmonisation of the management of patients with endometrial cancer across the different regions of Asia, drawing on the evidence provided by Western and Asian trials whilst respecting the variations in clinical presentation, diagnostic practices including molecular profiling and disparities in access to therapeutic options, including drug approvals and reimbursement strategies.All costs relating to this consensus conference were covered by the ESMO and the ISMPO from central dedicated funds. There was no external funding of the event or the manuscript production
Low energy excitations of double quantum dots in the lowest Landau level regime
We study the spectrum and magnetic properties of double quantum dots in the
lowest Landau level for different values of the hopping and Zeeman parameters
by means of exact diagonalization techniques in systems of N=6 and N=7
electrons and filling factor close to 2. We compare our results with those
obtained in double quantum layers and single quantum dots. The Kohn theorem is
also discussed.Comment: 23 pages, 4 figures, 1 table; references added; journal versio
Dynamics of the Compact, Ferromagnetic \nu=1 Edge
We consider the edge dynamics of a compact, fully spin polarized state at
filling factor . We show that there are two sets of collective
excitations localized near the edge: the much studied, gapless, edge
magnetoplasmon but also an additional edge spin wave that splits off below the
bulk spin wave continuum. We show that both of these excitations can soften at
finite wave-vectors as the potential confining the system is softened, thereby
leading to edge reconstruction by spin texture or charge density wave
formation. We note that a commonly employed model of the edge confining
potential is non-generic in that it systematically underestimates the texturing
instability.Comment: 13 pages, 7 figures, Revte
Olaparib maintenance monotherapy in platinum-sensitive relapsed ovarian cancer patients without a germline BRCA1/BRCA2 mutation: OPINION primary analysis
Maintenance; Olaparib; Ovarian cancerManteniment; Olaparib; Cà ncer d'ovarisMantenimiento; Olaparib; Cáncer de ovariosObjective
The phase IIIb OPINION trial (NCT03402841) investigated olaparib maintenance monotherapy in patients without a deleterious or suspected deleterious germline BRCA1/BRCA2 mutation (gBRCAm) who had platinum-sensitive relapsed ovarian cancer (PSROC) and had received ≥2 previous lines of platinum-based chemotherapy.
Methods
In this single-arm, open-label, international study, patients who had responded to platinum-based chemotherapy received maintenance olaparib tablets (300 mg twice daily) until disease progression or unacceptable toxicity. The primary endpoint was investigator-assessed progression-free survival (PFS) (modified RECIST version 1.1). A key secondary endpoint was PFS by homologous recombination deficiency (HRD) and somatic BRCAm (sBRCAm) status. The primary analysis of PFS was planned for 18 months after the last patient received their first dose.
Results
Two hundred and seventy-nine patients were enrolled and received olaparib. At data cutoff (October 2, 2020), 210 PFS events had occurred (75.3% maturity) and median PFS was 9.2 months (95% confidence interval [CI], 7.6–10.9) in the overall population. At 12 and 18 months, 38.5% and 24.3% of patients were progression-free, respectively. In the predefined biomarker subgroups, median PFS was 16.4, 11.1, 9.7, and 7.3 months in sBRCAm, HRD-positive including sBRCAm, HRD-positive excluding sBRCAm, and HRD-negative patients, respectively. The most common treatment-emergent adverse events (TEAEs) were nausea (48.4%) and fatigue/asthenia (44.1%). TEAEs led to dose interruption, dose reduction, and treatment discontinuation in 47.0%, 22.6%, and 7.5% of patients, respectively.
Conclusion
Maintenance olaparib demonstrated clinical benefit in patients without a gBRCAm, and across all subgroups, compared with historical placebo controls. There were no new safety signals.This study was funded by AstraZeneca and is part of an alliance between AstraZeneca and Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA
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