Measurement of B(D_s+ -> mu+ nu_mu)/B(D_s+ -> phi mu+ nu_mu) and Determination of the Decay Constant f_{D_s}

We have observed $23.2 \pm 6.0_{-0.9}^{+1.0}$ purely-leptonic decays of $D_s^+ -> \mu^+ \nu_\mu$ from a sample of muonic one prong decay events detected in the emulsion target of Fermilab experiment E653. Using the $D_s^+ -> \phi \mu^+ \nu_\mu$ yield measured previously in this experiment, we obtain $B(D_s^+ --> \mu^+ \nu_\mu) / B(D_s^+ --> \phi \mu^+ \nu_\mu) =0.16 \pm 0.06 \pm 0.03$. In addition, we extract the decay constant $f_{D_s}=194 \pm 35 \pm 20 \pm 14 MeV$.Comment: 15 pages including one figur

Psychology and aggression

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68264/2/10.1177_002200275900300301.pd

Finite-element method for time-dependent incompressible free surface flow

We present a finite-element method for time-dependent incompressible free surface fluid flow problems described by the Navier-Stokes equations. The elements chosen have dimensions in both space and time, and the resulting system of equations is block-tridiagonal and lends itself to solution by standard techniques. In the present article we restrict our attention to two-dimensional problems although three-dimensional problems may be solved by a straightforward generalization. The method is essentially an implicit time stepping technique and therefore stable even for relatively large time steps. With this choice of elements, the method is completely adaptive to the changing nature of the solution. An iterative procedure is used to find the position of the free surface; this procedure is found to be rapidly convergent determining accurately the shape of the free surface within a few iterations. Numerical results are given for the problem of entrainment of fluid by a vertically moving plate, which has applications to the chemical engineering problems of the free coating of metals. We also consider the problem of circulation flow in a rectangular channel

On the Complexity of UC Commitments

International audienceMotivated by applications to secure multiparty computation, we study the complexity of realizing universally composable (UC) commitments. Several recent works obtain practical UC commitment protocols in the common reference string (CRS) model under the DDH assumption. These protocols have two main disadvantages. First, even when applied to long messages, they can only achieve a small constant rate (namely, the communication complexity is larger than the length of the message by a large constant factor). Second, they require computationally expensive public-key operations for each block of each message being committed.Our main positive result is a UC commitment protocol that simultaneously avoids both of these limitations. It achieves an optimal rate of 1 (strictly speaking, 1 − o(1)) by making only few calls to an ideal oblivious transfer (OT) oracle and additionally making a black-box use of a (computationally inexpensive) PRG. By plugging in known efficient protocols for UC-secure OT, we get rate-1, computationally efficient UC commitment protocols under a variety of setup assumptions (including the CRS model) and under a variety of standard cryptographic assumptions (including DDH). We are not aware of any previous UC commitment protocols that achieve an optimal asymptotic rate.A corollary of our technique is a rate-1 construction for UC commitment length extension, that is, a UC commitment protocol for a long message using a single ideal commitment for a short message. The extension protocol additionally requires the use of a semi-honest (stand-alone) OT protocol. This raises a natural question: can we achieve UC commitment length extension while using only inexpensive PRG operations as is the case for stand-alone commitments and UC OT? We answer this question in the negative, showing that the existence of a semi-honest OT protocol is necessary (and sufficient) for UC commitment length extension. This shows, quite surprisingly, that UC commitments are qualitatively different from both stand-alone commitments and UC OT