Coarse-Grained Entanglement and Operator Growth in Anomalous Dynamics.

In two-dimensional Floquet systems, many-body localized dynamics in the bulk may give rise to a chaotic evolution at the one-dimensional edges that is characterized by a nonzero chiral topological index. Such anomalous dynamics is qualitatively different from local-Hamiltonian evolution. Here we show how the presence of a nonzero index affects entanglement generation and the spreading of local operators, focusing on the coarse-grained description of generic systems. We tackle this problem by analyzing exactly solvable models of random quantum cellular automata (QCA) that generalize random circuits. We find that a nonzero index leads to asymmetric butterfly velocities with different diffusive broadening of the light cones and to a modification of the order relations between the butterfly and entanglement velocities. We propose that these results can be understood via a generalization of the recently introduced entanglement membrane theory, by allowing for a spacetime entropy current, which in the case of a generic QCA is fixed by the index. We work out the implications of this current on the entanglement "membrane tension" and show that the results for random QCA are recovered by identifying the topological index with a background velocity for the coarse-grained entanglement dynamics.

Emergent SO(5) Symmetry at the Columnar Ordering Transition in the Classical Cubic Dimer Model.

The classical cubic-lattice dimer model undergoes an unconventional transition between a columnar crystal and a dimer liquid, in the same universality class as the deconfined quantum critical point in spin-1/2 antiferromagnets but with very different microscopic physics and microscopic symmetries. Using Monte Carlo simulations, we show that this transition has emergent SO(5) symmetry relating quantities characterizing the two phases. While the low-temperature phase has a conventional order parameter, the defining property of the Coulomb liquid on the high-temperature side is deconfinement of monomers, and so SO(5) relates fundamentally different types of objects. Studying linear system sizes up to L=96, we find that this symmetry applies with an excellent precision, consistently improving with system size over this range. It is remarkable that SO(5) emerges in a system as basic as the cubic dimer model, with only simple discrete degrees of freedom. Our results are important evidence for the generality of the SO(5) symmetry that has been proposed for the noncompact CP^{1} field theory. We describe an interpretation for these results in terms of a consistent hypothesis for the renormalization-group flow structure, allowing for the possibility that SO(5) may ultimately be a near-symmetry rather than exact.

Universality class of the two-dimensional polymer collapse transition.

The nature of the θ point for a polymer in two dimensions has long been debated, with a variety of candidates put forward for the critical exponents. This includes those derived by Duplantier and Saleur for an exactly solvable model. We use a representation of the problem via the CP^{N-1}σ model in the limit N→1 to determine the stability of this critical point. First we prove that the Duplantier-Saleur (DS) critical exponents are robust, so long as the polymer does not cross itself: They can arise in a generic lattice model and do not require fine-tuning. This resolves a longstanding theoretical question. We also address an apparent paradox: Two different lattice models, apparently both in the DS universality class, show different numbers of relevant perturbations, apparently leading to contradictory conclusions about the stability of the DS exponents. We explain this in terms of subtle differences between the two models, one of which is fine-tuned (and not strictly in the DS universality class). Next we allow the polymer to cross itself, as appropriate, e.g., to the quasi-two-dimensional case. This introduces an additional independent relevant perturbation, so we do not expect the DS exponents to apply. The exponents in the case with crossings will be those of the generic tricritical O(n) model at n=0 and different from the case without crossings. We also discuss interesting features of the operator content of the CP^{N-1} model. Simple geometrical arguments show that two operators in this field theory, with very different symmetry properties, have the same scaling dimension for any value of N (or, equivalently, any value of the loop fugacity). Also we argue that for any value of N the CP^{N-1} model has a marginal odd-parity operator that is related to the winding angle.

Topological Constraints in Directed Polymer Melts.

Polymers in a melt may be subject to topological constraints, as in the example of unlinked polymer rings. How to do statistical mechanics in the presence of such constraints remains a fundamental open problem. We study the effect of topological constraints on a melt of directed polymers, using simulations of a simple quasi-2D model. We find that fixing the global topology of the melt to be trivial changes the polymer conformations drastically. Polymers of length L wander in the transverse direction only by a distance of order (lnL)^{ζ} with ζ≃1.5. This is strongly suppressed in comparison with the Brownian L^{1/2} scaling which holds in the absence of the topological constraint. It is also much smaller than the predictions of standard heuristic approaches-in particular the L^{1/4} of a mean-field-like "array of obstacles" model-so our results present a sharp challenge to theory. Dynamics are also strongly affected by the constraints, and a tagged monomer in an infinite system performs logarithmically slow subdiffusion in the transverse direction. To cast light on the suppression of the strands' wandering, we analyze the topological complexity of subregions of the melt: the complexity is also logarithmically small, and is related to the wandering by a power law. We comment on insights the results give for 3D melts, directed and nondirected.

Azithromycin is not associated with QT prolongation in hospitalized patients with community-acquired pneumonia.

PURPOSE: Large data-based studies have reported excess cardiovascular mortality in high-risk patients treated with azithromycin, but whether or not azithromycin causes QT prolongation remains controversial. The purpose of this study was to examine the association of azithromycin treatment on QT prolongation in a cohort of patients hospitalized with community-acquired pneumonia (CAP) METHODS: One-hundred twenty-two hospitalized patients with CAP were enrolled in the study. We compared the baseline QTc, with daily post antibiotic QTc. Other risk factors for QT prolongation such as medication or electrolyte abnormalities were recorded. RESULTS: Ninety (73.8%) patients were treated with azithromycin (usually in combination with ceftriaxone), and 32 (26.2%) patients with other antibiotics (ampicillin-clavulanate, chloramphenicol, doxcycline, or ceftriaxone); 72.1% (88) of the cohort experienced QT lengthening; 72.7% with QT lengthening had a normal baseline QTc. Azithromycin was not associated with the post-antibiotic QTc. Wide (pathological) post-antibiotic QTc was associated with the pneumonia score. Every 10-point increase in the pneumonia score raised the risk for a pathological post antibiotic QTc by 1.249 (95%CI: 1.050-1.486). Analysis of patients with non-pathological baseline QTc revealed that pathological post-antibiotic QTc was only associated with previous stroke and not with the type of antibiotic. CONCLUSIONS: Azithromycin treatment was not associated with QT prolongation in patients with severe CAP. Nonetheless, in a large majority of hospitalized CAP patients, QT prolongation and pathological QTc develop regardless of the antibiotic used, especially in patients with previous stroke or a higher pneumonia score.

Emergent SO(5) Symmetry at the Néel to Valence-Bond-Solid Transition.

We show numerically that the "deconfined" quantum critical point between the Néel antiferromagnet and the columnar valence-bond solid, for a square lattice of spin 1/2, has an emergent SO(5) symmetry. This symmetry allows the Néel vector and the valence-bond solid order parameter to be rotated into each other. It is a remarkable (2+1)-dimensional analogue of the SO(4)=[SU(2)×SU(2)]/Z(2) symmetry that appears in the scaling limit for the spin-1/2 Heisenberg chain. The emergent SO(5) symmetry is strong evidence that the phase transition in the (2+1)-dimensional system is truly continuous, despite the violations of finite-size scaling observed previously in this problem. It also implies surprising relations between correlation functions at the transition. The symmetry enhancement is expected to apply generally to the critical two-component Abelian Higgs model (noncompact CP(1) model). The result indicates that in three dimensions there is an SO(5)-symmetric conformal field theory that has no relevant singlet operators, so is radically different from conventional Wilson-Fisher-type conformal field theories.

Bivalirudin versus Unfractionated Heparin during Percutaneous Coronary Intervention in Patients at High Risk for Bleeding.

Low/medium-bleeding-risk populations undergoing percutaneous coronary intervention (PCI) show significantly less bleeding with bivalirudin (BIV) than with unfractionated heparin (UFH), but this has not been established for high-risk patients. We performed a randomized double-blind prospective trial comparing efficacy and safety of BIV versus UFH combined with dual antiplatelet therapy during PCI among 100 high-risk patients with non-ST elevation myocardial infarction (NSTEMI) or angina pectoris. The baseline characteristics were similar in both treatment arms. A radial approach was used in 84% of patients with a higher rate in the BIV group (90 vs. 78%, p < 0.05). Study end points were: major and minor bleeding, port-of-entry complications, major adverse cardiac events (MACE) in-hospital, and at long-term follow-up. There was one case of major gastrointestinal bleeding in the BIV group and 7% minor bleeding complications in both categories. Rate of periprocedural myocardial infarction (PPMI) in the BIV group was twice that in the UFH group (20 vs. 10%, p < 0.16). In-hospital MACE rate was higher in BIV patients as well (12 vs. 2%, p = 0.1). By univariate analysis, the femoral approach was the predictor of PPMI and in-hospital MACE. In a multivariate model, the independent predictor of PPMI was previous MI (odds ratio, 7.7; p < 0.0158). PPMI was 49.7 times more likely with the femoral approach plus BIV than the nonfemoral approach plus UFH (p < 0.0021). At 41.5 ± 14 months' follow-up, end points did not significantly differ between the groups. In patients at high risk for bleeding undergoing PCI, BIV was not superior to UFH for bleeding complications, and early and late clinical outcomes.

Length distributions in loop soups.

Statistical lattice ensembles of loops in three or more dimensions typically have phases in which the longest loops fill a finite fraction of the system. In such phases it is natural to ask about the distribution of loop lengths. We show how to calculate moments of these distributions using CP(n-1) or RP(n-1) and O(n) σ models together with replica techniques. The resulting joint length distribution for macroscopic loops is Poisson-Dirichlet with a parameter θ fixed by the loop fugacity and by symmetries of the ensemble. We also discuss features of the length distribution for shorter loops, and use numerical simulations to test and illustrate our conclusions.

Universal statistics of vortex lines.

We study the vortex lines that are a feature of many random or disordered three-dimensional systems. These show universal statistical properties on long length scales, and geometrical phase transitions analogous to percolation transitions but in distinct universality classes. The field theories for these problems have not previously been identified, so that while many numerical studies have been performed, a framework for interpreting the results has been lacking. We provide such a framework with mappings to simple supersymmetric models. Our main focus is on vortices in short-range-correlated complex fields, which show a geometrical phase transition that we argue is described by the CP(k|k) model (essentially the CP(n-1) model in the replica limit n→1). This can be seen by mapping a lattice version of the problem to a lattice gauge theory. A related field theory with a noncompact gauge field, the 'NCCP(k|k) model', is a supersymmetric extension of the standard dual theory for the XY transition, and we show that XY duality gives another way to understand the appearance of field theories of this type. The supersymmetric descriptions yield results relevant, for example, to vortices in the XY model and in superfluids, to optical vortices, and to certain models of cosmic strings. A distinct but related field theory, the RP(2l|2l) model (or the RP(n-1) model in the limit n→1) describes the unoriented vortices that occur, for instance, in nematic liquid crystals. Finally, we show that in two dimensions, a lattice gauge theory analogous to that discussed in three dimensions gives a simple way to see the known relation between two-dimensional percolation and the CP(k|k) σ model with a θ term.

3D loop models and the CP(n-1) sigma model.

Many statistical mechanics problems can be framed in terms of random curves; we consider a class of three-dimensional loop models that are prototypes for such ensembles. The models show transitions between phases with infinite loops and short-loop phases. We map them to CP(n-1) sigma models, where n is the loop fugacity. Using Monte Carlo simulations, we find continuous transitions for n=1, 2, 3, and first order transitions for n≥5. The results are relevant to line defects in random media, as well as to Anderson localization and (2+1)-dimensional quantum magnets.

Implantation of a resynchronization implantable cardioverter defibrillator in a patient with persistent left superior vena cava.

Implantation of resynchronization implantable cardioverter defibrillator was performed in a patient with persistent left superior vena cava. A dual coil defibrillation lead was inserted in the right ventricle apex via a small innominate vein. Left ventricular and atrial leads were implanted through persistent left superior vena cava. Left ventricular lead was easily implanted into the postero lateral vein. Pacing thresholds and sensing values were excellent and remained stable at 18 months follow-up.Presence of persistent left superior vena cava generally makes transvenous lead implantation difficult. However when a favorable coronary sinus anatomy is also present, it may facilitate left ventricular lead positioning in the coronary sinus branches.

[Biphasic versus monophasic shock waveforms for transthoracic cardioversion of atrial flutter in the emergency room].

UNLABELLED: Transthoracic electrical cardioversion (ECV), traditionally using monophasic waveform (MW) shock, has an important role in the treatment of symptomatic atrial flutter (AFI). Biphasic waveform (BW) shock has been demonstrated to be more successful than MW shock for termination of atrial fibrillation, but data about its use for ECV of AFI are limited. METHODS AND RESULTS: We retrospectively analyzed the records of 53 patients (pts) admitted -to the ER due to symptomatic AFl during the period August 2004 to August 2005: 31 pts received BW shock and 22 pts MW shock. The type of shock waveforms and the initial energy of CV were chosen by the doctor on duty in the ER; the lower energy for ECV was 20 joules, which was increased to 50, 100 and 200 joules if necessary. There were no significant differences between the clinical characteristics of the pts who received BW shock or MW shock. All pts underwent ECV via anterior-laterally positioned hand-held electrode paddles. Successful ECV by BW shock and MW shock was 41% and 42% of the pts, respectively, using 20 joules of energy (p=n.s.); 77% and 80% using 50 joules (p=n.s.); 93% and 90% using 100 joules (p = n.s.); 100% of successful ECV was reached when 200 joules of energy was used, regardless of waveforms type. Median energy for successful ECV was 50 joules in both types of electrical waveforms. No complications were reported. CONCLUSIONS: There were no significant differences in the success rates of conversion of atrial flutter to sinus rhythm by BW or MW shock. We recommend 50 joules for starting energy of ECV of AF1 regardless of waveforms type.

Endocardial ventricular pacing through a bioprosthetic tricuspid valve.

A patient with bioprosthetic tricuspid valve was treated with ventricular endocardial pacing using a new delivery system consisting of a steerable catheter and a 4.1 F bipolar, fixed-screw, steroid eluting lead. The functioning of the lead and bioprosthetic tricuspid valve was excellent during the following year.

[Biphasic shock waveform for cardioversion of atrial fibrillation in the emergency room].

UNLABELLED: Transthoracic electrical cardioversion, traditionally monophasic shock waveform, has been a mainstay of the therapy for atrial fibrillation (AF) since its introduction into clinical practice. Recent studies have demonstrated that biphasic shock is more efficient than monophasic shock waveforms for terminating both ventricular fibrillation and AF; however, data on the recommended initial shock energy in conversion of AF by biphasic shocks are limited. AIM: Our study aimed to evaluate the optimal dose of the initial shock energy for conversion of AF to sinus rhythm by transthoracic biphasic shock waveforms in the Emergency Room (ER). METHODS AND RESULTS: A total of 144 consecutive patients, who came to the ER because of AF, were our study population. All patients underwent cardioversion via anterior-laterally positioned hand-held electrode paddles. Patients received sequential shocks of 50 J (only the first 40 patients), 100 J, 150 J and 200 J if necessary. There was a significantly greater cumulative conversion success rate with 100 J (70.5%) than 50 J shock energy (55%), p < 0.05; but even greater with 150 J (89%) than 100 J shock energy, p < 0.003; no significant difference was observed between 200 J (94%) and 150 J shock energy, p < 0.58. Nine of 12 patients, whose body weight was less than 70 kg, were successfully converted to sinus rhythm (75%) by 50 J shock 1 energy. After cardioversion there were reports of: a five seconds asystole observed in 1 patient; pulmonary edema in another patient; hypotension was reported in 1 patient and mild erythema in 14 patients (9.7%). CONCLUSION: Our findings support that biphasic waveform shock energy of 150 J is advised as a first attempt, but in patients with a body weight less than 70 kg. lower energy shock may be used.

Unsuccessful rescrewing of a dislodged screw-in atrial lead.

We report a case of unsuccessful rescrewing of an atrial lead after its early dislodgment in a 64 years old patient because of entrapped endocardial tissue in the screw-in system.

Incidence of postdischarge symptomatic paroxysmal atrial fibrillation in patients who underwent coronary artery bypass graft: long-term follow-up.

The aim of this retrospective study was to determine the incidence of symptomatic AF of patients who had undergone coronary artery bypass grafting (CABG) during long-term follow-up. The study population included 305 post-CABG patients who were regularly followed in the outpatient clinic. Paroxysmal AF (PAF) was defined as an episode of symptomatic AF when symptoms were prolonged enough for the patient to request medical care. Perioperative AF occurred in 88 (28.9%) patients. Postdischarge symptomatic PAF occurred in 25 (8.2%) patients with an annual incidence of 2% during a mean follow-up of 48 +/- 30 months. Eighteen (20.4%) patients also experienced perioperative AF with an annual incidence of 5.1%, while only 7 (3.2%) of 217 patients, without perioperative AF, had postdischarge AF (P < 0.0003). During long-term follow-up, postdischarge AF has a low incidence and prophylactic antiarrhythmic therapy is not recommended. The method of follow-up and retrospective analysis may understate PAF and even miss some symptomatic episodes. Perioperative AF is a predictor of symptomatic late PAF recurrences, particularly in patients with reduced left ventricular function.