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

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 $1<\nu <2$. 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

Dynamics of the Compact, Ferromagnetic \nu=1 Edge

We consider the edge dynamics of a compact, fully spin polarized state at filling factor $\nu=1$. 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

Spin-isospin textured excitations in a double layer at filling factor ν=2\nu =2

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 $\nu=1$ 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

Wigner Crystalline Edges in nu < 1 Quantum Dots

We investigate the edge reconstruction phenomenon believed to occur in quantum dots in the quantum Hall regime when the filling fraction is nu < 1. Our approach involves the examination of large dots (< 40 electrons) using a partial diagonalization technique in which the occupancies of the deep interior orbitals are frozen. To interpret the results of this calculation, we evaluate the overlap between the diagonalized ground state and a set of trial wavefunctions which we call projected necklace (PN) states. A PN state is simply the angular momentum projection of a maximum density droplet surrounded by a ring of localized electrons. Our calculations reveal that PN states have up to 99% overlap with the diagonalized ground states, and are lower in energy than the states identified in Chamon and Wen's study of the edge reconstruction.Comment: 8 pages, 8 figures, to be published in Phys. Rev.

Real-World Delivery of Rucaparib to Patients with Ovarian Cancer: Recommendations Based on an Integrated Safety Analysis of ARIEL2 and Study 10

Treatment options for women with recurrent ovarian cancer who have received two or more prior lines of chemotherapy have recently expanded with the U.S. Food and Drug Administration (FDA) and European Commission (EC) approvals of the poly(ADP‐ribose) polymerase (PARP) inhibitor rucaparib. As more oncologists begin to use rucaparib and other PARP inhibitors as part of routine clinical practice, awareness of possible side effects and how to adequately manage toxicities is crucial. In this review, we summarize the safety and tolerability of rucaparib reported in an integrated safety analysis that supported the FDA's initial approval of rucaparib in the treatment setting. Additionally, drawing on clinical data and our personal experience with rucaparib, we provide our recommendations on the management of common side effects observed with rucaparib, including anemia, blood creatinine elevations, alanine aminotransferase and aspartate aminotransferase elevations, thrombocytopenia, gastrointestinal‐related events (e.g., nausea, vomiting), and asthenia and fatigue. These side effects, many of which appear to be class effects of PARP inhibitors, are often self‐limiting and can be managed with adequate interventions such as treatment interruption and/or dose reduction and the use of supportive therapies. Supportive therapies may include blood transfusions for patients with anemia, prophylactic medications to prevent nausea and vomiting, or behavioral interventions to mitigate fatigue. Understanding and appropriate management of potential side effects associated with rucaparib may allow patients with ovarian cancer to continue to benefit from rucaparib treatment. Implications for Practice. Rucaparib was recently approved in the U.S. and European Union for use as treatment or maintenance for recurrent ovarian cancer. This review focuses on the safety and tolerability of rucaparib in the treatment setting. Similar side effects are observed in the maintenance setting. Drawing on the authors’ clinical experience with rucaparib, rucaparib prescribing information, and published supportive cancer care guidelines, this review discusses how to optimally manage common rucaparib‐associated side effects in patients with advanced ovarian cancer in the real‐world oncology setting. Adequate management of such side effects is crucial for allowing patients with ovarian cancer to remain on treatment to receive optimal efficacy benefit

Pushmepullyou: An efficient micro-swimmer

The swimming of a pair of spherical bladders that change their volumes and mutual distance is efficient at low Reynolds numbers and is superior to other models of artificial swimmers. The change of shape resembles the wriggling motion known as {\it metaboly} of certain protozoa.Comment: Minor rephrasing and changes in style; short explanations adde

Baryon Asymmetry, Dark Matter and Quantum Chromodynamics

We propose a novel scenario to explain the observed cosmological asymmetry between matter and antimatter, based on nonperturbative QCD physics. This scenario relies on a mechanism of separation of quarks and antiquarks in two coexisting phases at the end of the cosmological QCD phase transition: ordinary hadrons (and antihadrons), along with massive lumps (and antilumps) of novel color superconducting phase. The latter would serve as the cosmological cold dark matter. In certain conditions the separation of charge is C and CP asymmetric and can leave a net excess of hadrons over antihadrons in the conventional phase, even if the visible universe is globally baryon symmetric $B = 0$. In this case an equal, but negative, overall baryon charge must be hidden in the lumps of novel phase. Due to the small volume occupied by these dense lumps/antilumps of color superconducting phase and the specific features of their interaction with "normal" matter in hadronic phase, this scenario does not contradict the current phenomenological constrains on presence of antimatter in the visible universe. Moreover, in this scenario the observed cosmological ratio $\Omega_{DM}\sim\Omega_{B}$ within an order of magnitude finds a natural explanation, as both contributions to $\Omega$ originated from the same physics during the QCD phase transition. The baryon to entropy ratio $n_{B}/n_{\gamma}\sim 10^{-10}$ would also be a natural outcome, fixed by the temperature T_f \simlt T_{QCD} at which the separation of phases is completed.Comment: New paragraph added in subsection II.D; version to appear in Physical Review

θ−\theta- Parameter in 2 Color QCD at Finite Baryon and Isospin Density

We use 2-color QCD as a model to study the effects of simultaneous presence of the so-called $\theta$ parameter, chemical potentials for baryon number, $\mu_B$ and for isospin charge, $\mu_I$. We pay special attention to $\theta$, $\mu_B$, $\mu_I$ dependence of different vacuum condensates, including chiral and diquark condensates, as well as the gluon condensate, $$, and the topological susceptibility. We find that two phase transitions of the second order will occur when $\theta$ relaxes from $\theta=2\pi$ to $\theta=0$, if $\mu$ is of order of the pion mass. We demonstrate that the transition to the superfluid phase at $\theta = \pi$ occurs at a much lower chemical potential than at $\theta = 0$. We also show that the strong $\theta$ dependence present near $\theta = \pi$ in vacuum (Dashen's phenomenon), becomes smoothed out in the superfluid phase. Finally, we comment on the relevance of this study for the real world with N_c=3