38,256 research outputs found
Flavor and CP Violation with Fourth Generations Revisited
The Standard Model predicts a very small CP violation phase %= \arg M_{12} \simeq \arg\,(V^*_{ts}V_{tb})^2B_s\bar B_s\lambda^2\eta\Phi_{B_s}\sin2\Phi_{B_s}t'\Delta m_{B_s}{\cal B}(B \to X_s\ell^+\ell^-)f_{B_s}\sin2\Phi^{\rm
SM4}_{B_s} \sim -0.33m_{b'} = 4800.06 < |V_{t'b}| < 0.13\Gamma(Z\to b\bar b)\Delta m_{D}{\cal
B}(K^+\to\pi^+\nu\bar\nu){\cal
B}(K_L\to\pi^0\nu\bar\nu)V_{t'd}$.Comment: 8 pages, 11 figure
Algebraic Reduction of Feynman Diagrams to Scalar Integrals: a Mathematica implementation of LERG-I
A Mathematica implementation of the program LERG-I is presented that performs
the reduction of tensor integrals, encountered in one-loop Feynman diagram
calculations, to scalar integrals. The program was originally coded in REDUCE
and in that incarnation was applied to a number of problems of physical
interest.Comment: 16 page
The observed spiral structure of the Milky Way
The spiral structure of the Milky Way is not yet well determined. The keys to
understanding this structure are to increase the number of reliable spiral
tracers and to determine their distances as accurately as possible. HII
regions, giant molecular clouds (GMCs), and 6.7-GHz methanol masers are closely
related to high mass star formation, and hence they are excellent spiral
tracers. We update the catalogs of Galactic HII regions, GMCs, and 6.7-GHz
methanol masers, and then outline the spiral structure of the Milky Way. We
collected data for more than 2500 known HII regions, 1300 GMCs, and 900 6.7-GHz
methanol masers. If the photometric or trigonometric distance was not yet
available, we determined the kinematic distance using a Galaxy rotation curve
with the current IAU standard, = 8.5 kpc and = 220 km
s, and the most recent updated values of = 8.3 kpc and
= 239 km s, after we modified the velocities of tracers with the adopted
solar motions. With the weight factors based on the excitation parameters of
HII regions or the masses of GMCs, we get the distributions of these spiral
tracers. The distribution of tracers shows at least four segments of arms in
the first Galactic quadrant, and three segments in the fourth quadrant. The
Perseus Arm and the Local Arm are also delineated by many bright HII regions.
The arm segments traced by massive star forming regions and GMCs are able to
match the HI arms in the outer Galaxy. We found that the models of three-arm
and four-arm logarithmic spirals are able to connect most spiral tracers. A
model of polynomial-logarithmic spirals is also proposed, which not only
delineates the tracer distribution, but also matches the observed tangential
directions.Comment: 22 Pages, 16 Figures, 7 Tables, updated to match the published
versio
Noise-induced vortex reversal of self-propelled particles
We report an interesting phenomenon of noise-induced vortex reversal in a
two-dimensional system of self-propelled particles (SPP) with soft-core
interactions. With the aid of forward flux sampling, we analyze the
configurations along the reversal pathway and thus identify the mechanism of
vortex reversal. We find that statistically the reversal exhibits a
hierarchical process: those particles at the periphery first change their
motion directions, and then more inner layers of particles reverse later on.
Furthermore, we calculate the dependence of the average reversal rate on noise
intensity and the number of SPP. We find that the rate decreases
exponentially with the reciprocal of . Interestingly, the rate varies
nonmonotonically with and a minimal rate exists for an intermediate value
of .Comment: 4 pages, 5 figure
Infinite Hopf family of elliptic algebras and bosonization
Elliptic current algebras E_{q,p}(\hat{g}) for arbitrary simply laced finite
dimensional Lie algebra g are defined and their co-algebraic structures are
studied. It is shown that under the Drinfeld like comultiplications, the
algebra E_{q,p}(\hat{g}) is not co-closed for any g. However putting the
algebras E_{q,p}(\hat{g}) with different deformation parameters together, we
can establish a structure of infinite Hopf family of algebras. The level 1
bosonic realization for the algebra E_{q,p}(\hat{g}) is also established.Comment: LaTeX, 11 pages. This is the new and final versio
Robust pricing and hedging under trading restrictions and the emergence of local martingale models
We consider the pricing of derivatives in a setting with trading
restrictions, but without any probabilistic assumptions on the underlying
model, in discrete and continuous time. In particular, we assume that European
put or call options are traded at certain maturities, and the forward price
implied by these option prices may be strictly decreasing in time. In discrete
time, when call options are traded, the short-selling restrictions ensure no
arbitrage, and we show that classical duality holds between the smallest
super-replication price and the supremum over expectations of the payoff over
all supermartingale measures. More surprisingly in the case where the only
vanilla options are put options, we show that there is a duality gap. Embedding
the discrete time model into a continuous time setup, we make a connection with
(strict) local-martingale models, and derive framework and results often seen
in the literature on financial bubbles. This connection suggests a certain
natural interpretation of many existing results in the literature on financial
bubbles
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