Local-duality QCD sum rules for strong isospin breaking in the decay constants of heavy–light mesons

We discuss the leptonic decay constants of heavy–light mesons by means of Borel QCD sum rules in the local-duality (LD) limit of infinitely large Borel mass parameter. In this limit, for an appropriate choice of the invariant structures in the QCD correlation functions, all vacuum-condensate contributions vanish and all nonperturbative effects are contained in only one quantity, the effective threshold. We study properties of the LD effective thresholds in the limits of large heavy-quark mass \(m_Q\) and small light-quark mass \(m_q\). In the heavy-quark limit, we clarify the role played by the radiative corrections in the effective threshold for reproducing the pQCD expansion of the decay constants of pseudoscalar and vector mesons. We show that the dependence of the meson decay constants on \(m_q\) arises predominantly (at the level of 70–80%) from the calculable \(m_q\)-dependence of the perturbative spectral densities. Making use of the lattice QCD results for the decay constants of nonstrange and strange pseudoscalar and vector heavy mesons, we obtain solid predictions for the decay constants of heavy–light mesons as functions of \(m_q\) in the range from a few to 100 MeV and evaluate the corresponding strong isospin-breaking effects: \(f_{D^+} - f_{D^0}=(0.96 \pm 0.09) \ \mathrm{MeV}\), \(f_{D^{*+}} - f_{D^{*0}}= (1.18 \pm 0.35) \ \mathrm{MeV}\), \(f_{B^0} - f_{B^+}=(1.01 \pm 0.10) \ \mathrm{MeV}\), \(f_{B^{*0}} - f_{B^{*+}}=(0.89 \pm 0.30) \ \mathrm{MeV}\).     

Observations on sound propagation in rapidly rotating Bose-Einstein condensates

Repulsive laser potential pulses applied to vortex lattices of rapidly rotating Bose-Einstein condensates create propagating density waves which we have observed experimentally and modeled computationally to high accuracy. We have observed a rich variety of dynamical phenomena ranging from interference effects and shock-wave formation to anisotropic sound propagation.     

Review of lattice results concerning low-energy particle physics

We review lattice results relevant for pion and kaon physics with the aim of making them easily accessible to the particle physics community. Specifically, we review the determination of the light-quark masses, the form factor f ₊(0), relevant for the semileptonic K→π transition at zero momentum transfer as well as the ratio f _K /f _π of decay constants and discuss the consequences for the elements V _us and V _ud of the CKM matrix. Furthermore, we describe the results obtained on the lattice for some of the low-energy constants of SU(2) _L ×SU(2) _R and SU(3) _L ×SU(3) _R Chiral Perturbation Theory and review the determination of the B _K parameter of neutral kaon mixing. We introduce quality criteria and use these when forming averages. Although subjective and imperfect, these criteria may help the reader to judge different aspects of current lattice computations. Our main results are summarized in Sect. 1.2, but we stress the importance of the detailed discussion that underlies these results and constitutes the bulk of the present review.     

On the critical point of an interacting two-dimensional trapped Bose gas

We consider a quantized vortex excitation in a two-dimensional, harmonically trapped Bose gas and derive an equation for the Berezinskii-Kosterlitz-Thouless transition temperature based on a simple free-energy argument. We relate the critical phase-space density at the transition to the ratio between the entropy gain and the corresponding cost in energy of creating a free vortex excitation in the system.     

Thermal activation of vortex-antivortex pairs in quasi-two-dimensional Bose-Einstein condensates

Here we show, by performing ab initio classical field simulations that two distinct superfluid phases, separated by thermal vortex-antivortex pair creation, exist in experimentally producible quasi-2D Bose gas. These results resolve the debate on the nature of the low temperature phase(s) of a trapped interacting 2D Bose gas.     

Giant vortex lattice deformations in rapidly rotating bose-einstein condensates

We have performed numerical simulations of giant vortex structures in rapidly rotating Bose-Einstein condensates within the Gross-Pitaevskii formalism. We reproduce the qualitative features, such as oscillation of the giant vortex core area, formation of toroidal density hole, and the precession of giant vortices, observed in the recent experiment [Phys. Rev. Lett., ()]]. We provide a mechanism which quantitatively explains the observed core oscillation phenomenon. We demonstrate the clear distinction between the mechanism of atom removal and a repulsive pinning potential in creating giant vortices. In addition, we have been able to simulate the transverse Tkachenko vortex lattice vibrations.     

Methacrylic Zwitterionic,Thermoresponsive, and Hydrophilic (Co)Polymers via Cu(0)‐Polymerization: The Importance of Halide Salt Additives

The synthesis of hydrophilic, thermoresponsive, and zwitterionic polymethacrylates is reported by Cu(0)‐mediated reversible deactivation radical polymerization in water and/or water/alcohol mixtures. The predisproportionation of [Cu^I(PMDETA)Cl] in water prior to initiator and monomer addition is exploited to yield well‐defined polymethacrylates with full monomer conversions in 30 min. The addition of supplementary halide salts (NaCl) enables the synthesis of various molecular weight poly[poly(ethylene glycol) methyl ether methacrylate] (PEGMA₄₇₅) (DP_n = 10–80, M_n ≈ 10 000–40 000 g mol⁻¹) with full monomer conversion and narrow molecular weight distributions attained in all cases (Đ ≈ 1.20–1.30). A bifunctional PEG initiator (average M_n ≈ 1000 g mol⁻¹) is utilized for the polymerization of a wide range of methacrylates including 2‐dimethylaminoethyl methacrylate, 2‐morpholinoethyl methacrylate, [2‐(methacryloyloxy)ethyl]dimethyl‐(3‐sulfopropyl)ammonium hydroxide, and 2‐methacryloyloxyethyl phosphorylcholine. Despite the high water content, high end group fidelity is demonstrated by in situ chain extensions and block copolymerizations with PEGMA₄₇₅ yielding well‐defined functional telechelic pentablock copolymers within 2.5 h.

     

Structure and stability of vortices in dilute Bose-Einstein condensates at ultralow temperatures

We compute the structure of a quantized vortex line in a harmonically trapped dilute atomic Bose-Einstein condensate using the Popov version of the Hartree-Fock-Bogoliubov mean-field theory. The vortex is shown to be (meta)stable in a nonrotating trap even in the zero-temperature limit, thus confirming that weak particle interactions induce for the condensed gas a fundamental property characterizing "classical" superfluids. We present the structure of the vortex at ultralow temperatures and discuss the crucial effect of the thermal gas component to its energetic stability.     

Extraction of ground-state decay constant from dispersive sum rules: QCD vs potential models

We compare the extraction of the ground-state decay constant from the two-point correlator in QCD and in potential models and show that the results obtained at each step of the extraction procedure follow a very similar pattern. We prove that allowing for a Borel-parameter-dependent effective continuum threshold yields two essential improvements compared to employing a Borel-parameter-independent quantity: (i) It reduces considerably the (unphysical) dependence of the extracted bound-state mass and the decay constant on the Borel parameter. (ii) In a potential model, where the actual value of the decay constant is known from the Schrödinger equation, a Borel-parameter-dependent threshold leads to an improvement of the accuracy of the extraction procedure. Our findings suggest that in QCD a Borel-parameter-dependent threshold leads to a more reliable and accurate determination of bound-state characteristics by the method of sum rules.