5,992 research outputs found
Constraint on the branching ratio of B_c \to tau nu from LEP1 and consequences for R(D(*)) anomaly
Recently there has been interest in the correlation between R(D*) and the
branching ratio (BR) of in models with a charged scalar
H^\pm. Any enhancement of R(D*) by alone (in order to agree with
current data) also enhances ), for which there has been no
direct search at hadron colliders. We show that LEP data taken at the Z peak
requires BR() < 10%, and this constraint is significantly
stronger than the recent constraint BR() < 30% from
considering the lifetime of B_c. In order to respect this new constraint, any
explanation of the R(D) and R(D*) anomaly in terms of alone would
require the future measurements of R(D*) to be even closer to the Standard
Model prediction. A stronger limit on BR() (or its first
measurement) would be obtained if the L3 collaboration used all its data taken
at the Z peak.Comment: 14 pages, 4 figures, a reference and two sentences adde
Three-particle bound states in a finite volume: unequal masses and higher partial waves
An explicit expression for the finite-volume energy shift of shallow
three-body bound states for non-identical particles is obtained in the unitary
limit. The inclusion of the higher partial waves is considered. To this end,
the method of arXiv:1412.4969 (Mei{\ss}ner et al.) is generalized for the case
of unequal masses and arbitrary angular momenta. It is shown that in the S-wave
and in the equal mass limit, the result from arXiv:1412.4969 is reproduced.Comment: 17 pages, 1 figur
A bounded degree SOS hierarchy for polynomial optimization
We consider a new hierarchy of semidefinite relaxations for the general
polynomial optimization problem on a
compact basic semi-algebraic set . This hierarchy combines some
advantages of the standard LP-relaxations associated with Krivine's positivity
certificate and some advantages of the standard SOS-hierarchy. In particular it
has the following attractive features: (a) In contrast to the standard
SOS-hierarchy, for each relaxation in the hierarchy, the size of the matrix
associated with the semidefinite constraint is the same and fixed in advance by
the user. (b) In contrast to the LP-hierarchy, finite convergence occurs at the
first step of the hierarchy for an important class of convex problems. Finally
(c) some important techniques related to the use of point evaluations for
declaring a polynomial to be zero and to the use of rank-one matrices make an
efficient implementation possible. Preliminary results on a sample of non
convex problems are encouraging
Long-distance entanglement generation with scalable and robust two-dimensional quantum network
We present a protocol for generating entanglement over long distances in a
two-dimensional quantum network based on the surface error-correction code.
This protocol requires a fixed number of quantum memories at each node of the
network and tolerates error rates of up to 1.67% in the quantum channels.Comment: 5 pags, 4 figs. V2: text corrected, discussion on channel losses
added. Accepted by PR
A Pure Test for the Elasticity of Yield Spreads
The correlation between interest rates and corporate bond yield spreads is a well-known feature of structural bond pricing models. Duffee (1998) argues that this correlation is weak once the effects of call options are removed from the data; a conclusion that contradicts the negative correlation expected by Longstaff and Schwartz (1995). However, Elton et al. (2001) point out that Duffee's analysis ignores the effects of the tax differential between U.S. Treasury and corporate bonds. Canadian bonds have no such tax differential, yet, after controlling for callability, we find that the correlation between interest rates and corporate bond spreads remains negligible. We also find a significant negative relationship for callable bonds with this relationship increasing with the moneyness of the call provision. These results are robust under alternate empirical specifications.Bond Yield Spread, Default Risk, Callable Bonds, Corporate Bonds
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