1,114 research outputs found
Probing Supersymmetric Flavor Models with
We discuss the supersymmetric contribution to in various
supersymmetric flavor models. We find that in alignment models the
supersymmetric contribution could be significant while in heavy squark models
it is expected to be small. The situation is particularly interesting in models
that solve the flavor problems by either of the above mechanisms and the
remaining CP problems by means of approximate CP, that is, all CP violating
phases are small. In such models, the standard model contributions cannot
account for and a failure of the supersymmetric
contributions to do so would exclude the model. In models of alignment and
approximate CP, the supersymmetric contributions can account for
only if both the supersymmetric model parameters and the
hadronic parameters assume rather extreme values. Such models are then strongly
disfavored by the measurements. Models of heavy squarks
and approximate CP are excluded.Comment: 16 pages, harvmac. v2: We added a discussion of the intriguing
implications that would follow if a recent lattice result is confirme
Coseismic horizontal slip revealed by sheared clastic dikes in the Dead Sea Basin
Peer reviewedPostprin
Statistical determination of the length dependence of high-order polarization mode dispersion
We describe a method of characterizing high-order polarization mode dispersion (PMD).Using a new expansion to approximate the Jones matrix of a polarization-dispersive medium, we study the length dependence of high-order PMD to the fourth order. A simple rule for the asymptotic behavior of PMD for short and long fibers is found. It is also shown that, in long fibers (~1000 km), at 40 Gbits/s the third- and fourth-order PMD may become comparable to the second-order PMD
On the number of rectangulations of a planar point set
AbstractWe investigate the number of different ways in which a rectangle containing a set of n noncorectilinear points can be partitioned into smaller rectangles by n (nonintersecting) segments, such that every point lies on a segment. We show that when the relative order of the points forms a separable permutation, the number of rectangulations is exactly the (n+1)st Baxter number. We also show that no matter what the order of the points is, the number of guillotine rectangulations is always the nth Schröder number, and the total number of rectangulations is O(20n/n4)
B-factory Signals for a Warped Extra Dimension
We study predictions for B-physics in a class of models, recently introduced,
with a non-supersymmetric warped extra dimension. In these models few () TeV Kaluza-Klein masses are consistent with electroweak data due to bulk
custodial symmetry. Furthermore, there is an analog of GIM mechanism which is
violated by the heavy top quark (just as in SM) leading to striking signals at
-factories:(i) New Physics (NP) contributions to transitions
are comparable to SM. This implies that, within this NP framework, the success
of SM unitarity triangle fit is a ``coincidence'' Thus, clean extractions of
unitarity angles via e.g. are likely to
be affected, in addition to O(1) deviation from SM prediction in mixing.
(ii) O(1) deviation from SM predictions for in rate as well
as in forward-backward and direct CP asymmetry. (iii) Large mixing-induced CP
asymmetry in radiative B decays, wherein the SM unamibgously predicts very
small asymmetries. Also with KK masses 3 TeV or less, and with anarchic Yukawa
masses, contributions to electric dipole moments of the neutron are roughly 20
times larger than the current experimental bound so that this framework has a
"CP problem".Comment: On further consideration, we found that our framework does have a "CP
problem" in that though contributions to neutron's electric dipole moment
from CKM-like phases vanish at the one-loop level, sizeable contributions are
induced by Majorana-like phases. Last sentence of abstract is changed along
with para #3 and 4 on page
Colordag: An Incentive-Compatible Blockchain
We present Colordag, a blockchain protocol where following the prescribed
strategy is, with high probability, a best response as long as all miners have
less than 1/2 of the mining power. We prove the correctness of Colordag even if
there is an extremely powerful adversary who knows future actions of the
scheduler: specifically, when agents will generate blocks and when messages
will arrive. The state-of-the-art protocol, Fruitchain, is an epsilon-Nash
equilibrium as long as all miners have less than 1/2 of the mining power.
However, there is a simple deviation that guarantees that deviators are never
worse off than they would be by following Fruitchain, and can sometimes do
better. Thus, agents are motivated to deviate. Colordag implements a solution
concept that we call epsilon-sure Nash equilibrium and does not suffer from
this problem. Because it is an epsilon-sure Nash equilibrium, Colordag is an
epsilon Nash equilibrium and with probability (1 - epsilon) is a best response.Comment: To be published in DISC 202
BCC vs. HCP - The Effect of Crystal Symmetry on the High Temperature Mobility of Solid He
We report results of torsional oscillator (TO) experiments on solid He at
temperatures above 1K. We have previously found that single crystals, once
disordered, show some mobility (decoupled mass) even at these rather high
temperatures. The decoupled mass fraction with single crystals is typically 20-
30%. In the present work we performed similar measurements on polycrystalline
solid samples. The decoupled mass with polycrystals is much smaller, 1%,
similar to what is observed by other groups. In particular, we compared the
properties of samples grown with the TO's rotation axis at different
orientations with respect to gravity. We found that the decoupled mass fraction
of bcc samples is independent of the angle between the rotation axis and
gravity. In contrast, hcp samples showed a significant difference in the
fraction of decoupled mass as the angle between the rotation axis and gravity
was varied between zero and 85 degrees. Dislocation dynamics in the solid
offers one possible explanation of this anisotropy.Comment: 10 pages, 5 figures, to appear in Journal of Low Temperature Physics
- special issue on Supersolidit
Fairness and Efficiency in DAG-based Cryptocurrencies
Bitcoin is a decentralised digital currency that serves as an alternative to
existing transaction systems based on an external central authority for
security. Although Bitcoin has many desirable properties, one of its
fundamental shortcomings is its inability to process transactions at high
rates. To address this challenge, many subsequent protocols either modify the
rules of block acceptance (longest chain rule) and reward, or alter the
graphical structure of the public ledger from a tree to a directed acyclic
graph (DAG). Motivated by these approaches, we introduce a new general
framework that captures ledger growth for a large class of DAG-based
implementations. With this in hand, and by assuming honest miner behaviour, we
(experimentally) explore how different DAG-based protocols perform in terms of
fairness, i.e., if the block reward of a miner is proportional to their hash
power, as well as efficiency, i.e. what proportion of user transactions a
ledger deems valid after a certain length of time. Our results demonstrate
fundamental structural limits on how well DAG-based ledger protocols cope with
a high transaction load. More specifically, we show that even in a scenario
where every miner on the system is honest in terms of when they publish blocks,
what they point to, and what transactions each block contains, fairness and
efficiency of the ledger can break down at specific hash rates if miners have
differing levels of connectivity to the P2P network sustaining the protocol
- …