Vortex-lattice melting in a one-dimensional optical lattice

We investigate quantum fluctuations of a vortex lattice in a one-dimensional optical lattice. Our method gives full access to all the modes of the vortex lattice and we discuss in particular the Bloch bands of the Tkachenko modes. Because of the small number of particles in the pancake Bose-Einstein condensates at every site of the optical lattice, finite-size effects become very important. Therefore, the fluctuations in the vortex positions are inhomogeneous and the melting of the lattice occurs from the outside inwards. Tunneling between neighbouring pancakes substantially reduces the inhomogeneity as well as the size of the fluctuations.Comment: 4 pages, 4 figure

Ultracold Superstrings in atomic boson-fermion mixtures

We propose a setup with ultracold atomic gases that can be used to make a nonrelativistic superstring in four spacetime dimensions. In particular, we consider for the creation of the superstring a fermionic atomic gas that is trapped in the core of a vortex in a Bose-Einstein condensate. We explain the required tuning of experimental parameters to achieve supersymmetry between the fermionic atoms and the bosonic modes describing the oscillations in the vortex position. Furthermore, we discuss the experimental consequences of supersymmetry.Comment: 4 pages, 4 figures; published versio

Real-World Repetition Estimation by Div, Grad and Curl

We consider the problem of estimating repetition in video, such as performing push-ups, cutting a melon or playing violin. Existing work shows good results under the assumption of static and stationary periodicity. As realistic video is rarely perfectly static and stationary, the often preferred Fourier-based measurements is inapt. Instead, we adopt the wavelet transform to better handle non-static and non-stationary video dynamics. From the flow field and its differentials, we derive three fundamental motion types and three motion continuities of intrinsic periodicity in 3D. On top of this, the 2D perception of 3D periodicity considers two extreme viewpoints. What follows are 18 fundamental cases of recurrent perception in 2D. In practice, to deal with the variety of repetitive appearance, our theory implies measuring time-varying flow and its differentials (gradient, divergence and curl) over segmented foreground motion. For experiments, we introduce the new QUVA Repetition dataset, reflecting reality by including non-static and non-stationary videos. On the task of counting repetitions in video, we obtain favorable results compared to a deep learning alternative

Initial-State Radiation Measurement of the e+e−−>π+π−π+π− Cross Section

We study the process e+e-→π+π-π+π-γ, with a photon emitted from the initial-state electron or positron, using 454.3  fb-1 of data collected with the BABAR detector at SLAC, corresponding to approximately 260 000 signal events. We use these data to extract the nonradiative σ(e+e-→π+π-π+π-) cross section in the energy range from 0.6 to 4.5 GeV. The total uncertainty of the cross section measurement in the peak region is less than 3%, higher in precision than the corresponding results obtained from energy scan data

Search for the Z1(4050)+ and Z2(4250)+ states in Bˉ0→χc1K−π+ and B+→χc1K0Sπ+

We search for the Z1(4050)+ and Z2(4250)+ states, reported by the Belle Collaboration, decaying to χc1π+ in the decays B̅ 0→χc1K-π+ and B+→χc1KS0π+ where χc1→J/ψγ. The data were collected with the BABAR detector at the SLAC PEP-II asymmetric-energy e+e- collider operating at center-of-mass energy 10.58 GeV, and correspond to an integrated luminosity of 429  fb-1. In this analysis, we model the background-subtracted, efficiency-corrected χc1π+ mass distribution using the Kπ mass distribution and the corresponding normalized Kπ Legendre-polynomial moments, and then test the need for the inclusion of resonant structures in the description of the χc1π+ mass distribution. No evidence is found for the Z1(4050)+ and Z2(4250)+ resonances, and 90% confidence level upper limits on the branching fractions are reported for the corresponding B-meson decay modes

Tubelet-Contrastive Self-Supervision for Video-Efficient Generalization

We propose a self-supervised method for learning motion-focused video representations. Existing approaches minimize distances between temporally augmented videos, which maintain high spatial similarity. We instead propose to learn similarities between videos with identical local motion dynamics but an otherwise different appearance. We do so by adding synthetic motion trajectories to videos which we refer to as tubelets. By simulating different tubelet motions and applying transformations, such as scaling and rotation, we introduce motion patterns beyond what is present in the pretraining data. This allows us to learn a video representation that is remarkably data efficient: our approach maintains performance when using only 25% of the pretraining videos. Experiments on 10 diverse downstream settings demonstrate our competitive performance and generalizability to new domains and fine-grained actions. Code is available at https://github.com/fmthoker/tubelet-contrast

Search for b→u transitions in B±→[K∓π±π0]DK± decays

We present a study of the decays B±→DK± with D mesons reconstructed in the K+π-π0 or K-π+π0 final states, where D indicates a D0 or a D̅ 0 meson. Using a sample of 474×106 BB̅ pairs collected with the BABAR detector at the PEP-II asymmetric-energy e+e- collider at SLAC, we measure the ratios R±≡Γ(B±→[K∓π±π0]DK±)/Γ(B±→[K±π∓π0]DK±). We obtain R+=(5-10+12(stat)-4+2(syst))×10-3 and R-=(12-10+12(stat)-5+3(syst))×10-3, from which we extract the upper limits at 90% probability: R+<23×10-3 and R-<29×10-3. Using these measurements, we obtain an upper limit for the ratio rB of the magnitudes of the b→u and b→c amplitudes rB<0.13 at 90% probability