16,103 research outputs found
A bibliometric index based on the complete list of cited Publications
We propose a new index, the j-index, which is defined for an author as the sum of the square roots of the numbers of citations to each of the author’s publications. The idea behind the j-index it to remedy a drawback of the h-index - that the h-index does not take into account the full citation record of a researcher. The square root function is motivated by our desire to avoid the possible bias that may occur with a simple sum when an author has several very highly cited papers. We compare the j-index to the h-index, the g-index and the total citation count for three subject areas using several association measures. Our results indicate that that the association between the j-index and the other indices varies according to the subject area. One explanation of this variation may be due to the proportion of citations to publications of the researcher that are in the h-core. The j-index is not an h-index variant, and as such is intended to complement rather than necessarily replace the h-index and other bibliometric indicators, thus providing a more complete picture of a researcher’s achievements
Identification and stochastic control of helicopter dynamic modes
A general treatment of parameter identification and stochastic control for use on helicopter dynamic systems is presented. Rotor dynamic models, including specific applications to rotor blade flapping and the helicopter ground resonance problem are emphasized. Dynamic systems which are governed by periodic coefficients as well as constant coefficient models are addressed. The dynamic systems are modeled by linear state variable equations which are used in the identification and stochastic control formulation. The pure identification problem as well as the stochastic control problem which includes combined identification and control for dynamic systems is addressed. The stochastic control problem includes the effect of parameter uncertainty on the solution and the concept of learning and how this is affected by the control's duel effect. The identification formulation requires algorithms suitable for on line use and thus recursive identification algorithms are considered. The applications presented use the recursive extended kalman filter for parameter identification which has excellent convergence for systems without process noise
Drift rate control of a Brownian processing system
A system manager dynamically controls a diffusion process Z that lives in a
finite interval [0,b]. Control takes the form of a negative drift rate \theta
that is chosen from a fixed set A of available values. The controlled process
evolves according to the differential relationship dZ=dX-\theta(Z) dt+dL-dU,
where X is a (0,\sigma) Brownian motion, and L and U are increasing processes
that enforce a lower reflecting barrier at Z=0 and an upper reflecting barrier
at Z=b, respectively. The cumulative cost process increases according to the
differential relationship d\xi =c(\theta(Z)) dt+p dU, where c(\cdot) is a
nondecreasing cost of control and p>0 is a penalty rate associated with
displacement at the upper boundary. The objective is to minimize long-run
average cost. This problem is solved explicitly, which allows one to also solve
the following, essentially equivalent formulation: minimize the long-run
average cost of control subject to an upper bound constraint on the average
rate at which U increases. The two special problem features that allow an
explicit solution are the use of a long-run average cost criterion, as opposed
to a discounted cost criterion, and the lack of state-related costs other than
boundary displacement penalties. The application of this theory to power
control in wireless communication is discussed.Comment: Published at http://dx.doi.org/10.1214/105051604000000855 in the
Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute
of Mathematical Statistics (http://www.imstat.org
Models and Phenomenology of Maximal Flavor Violation
We consider models of maximal flavor violation (MxFV), in which a new scalar
mediates large q_3 q_1 or q_3 q_2 flavor changing transitions (q_i is
an i'th generation quark), while q_3 q_3 transitions are suppressed, e.g.,
\xi_{31}, \xi_{13} ~ V_{tb} and \xi_{33} ~ V_{td}, where \xi_{ij} are the new
scalar couplings to quarks and V is the CKM matrix. We show that, contrary to
the conventional viewpoint, such models are not ruled out by the existing low
energy data on K^0, B^0 and D^0 oscillations and rare K and B-decays. We also
show that these models of MxFV can have surprising new signatures at the LHC
and the Tevatron.Comment: Latex, 4 pages, 1 figure. Version as publishe
Quantum random walks without walking
Quantum random walks have received much interest due to their non-intuitive
dynamics, which may hold the key to a new generation of quantum algorithms.
What remains a major challenge is a physical realization that is experimentally
viable and not limited to special connectivity criteria. We present a scheme
for walking on arbitrarily complex graphs, which can be realized using a
variety of quantum systems such as a BEC trapped inside an optical lattice.
This scheme is particularly elegant since the walker is not required to
physically step between the nodes; only flipping coins is sufficient.Comment: 12 manuscript pages, 3 figure
Absence of dynamical localization in interacting driven systems
Using a numerically exact method we study the stability of dynamical
localization to the addition of interactions in a periodically driven isolated
quantum system which conserves only the total number of particles. We find that
while even infinitesimally small interactions destroy dynamical localization,
for weak interactions density transport is significantly suppressed and is
asymptotically diffusive, with a diffusion coefficient proportional to the
interaction strength. For systems tuned away from the dynamical localization
point, even slightly, transport is dramatically enhanced and within the largest
accessible systems sizes a diffusive regime is only pronounced for sufficiently
small detunings.Comment: Scipost resubmission. 14 pages, 4 figures. Changes to the figures.
Corrects a few typo
Efficiency at optimal work from finite reservoirs: a probabilistic perspective
We revisit the classic thermodynamic problem of maximum work extraction from
two arbitrary sized hot and cold reservoirs, modelled as perfect gases.
Assuming ignorance about the extent to which the process has advanced, which
implies an ignorance about the final temperatures, we quantify the prior
information about the process and assign a prior distribution to the unknown
temperature(s). This requires that we also take into account the temperature
values which are regarded to be unphysical in the standard theory, as they lead
to a contradiction with the physical laws. Instead in our formulation, such
values appear to be consistent with the given prior information and hence are
included in the inference. We derive estimates of the efficiency at optimal
work from the expected values of the final temperatures, and show that these
values match with the exact expressions in the limit when any one of the
reservoirs is very large compared to the other. For other relative sizes of the
reservoirs, we suggest a weighting procedure over the estimates from two valid
inference procedures, that generalizes the procedure suggested earlier in [J.
Phys. A: Math. Theor. {\bf 46}, 365002 (2013)]. Thus a mean estimate for
efficiency is obtained which agrees with the optimal performance to a high
accuracy.Comment: 14 pages, 6 figure
Proposing "b-Parity" - a New Approximate Quantum Number in Inclusive b-jet Production - as an Efficient Probe of New Flavor Physics
We consider the inclusive reaction \ell^+ \ell^- -> nb +X (n = number of
b-jets) in lepton colliders for which we propose a useful approximately
conserved quantum number b_P=(-1)^n that we call b-Parity (b_P). We make the
observation that the Standard Model (SM) is essentially b_P-even since SM
b_P-violating signals are necessarily CKM suppressed. In contrast new flavor
physics can produce b_P=-1 signals whose only significant SM background is due
to b-jet misidentification. Thus, we show that b-jet counting, which relies
primarily on b-tagging, becomes a very simple and sensitive probe of new flavor
physics (i.e., of b_P-violation).Comment: 5 pages using revtex, 2 figures embadded in the text using epsfig. As
will appear in Phys.Rev.Lett.. Considerable improvement was made in the
background calculation as compared to version 1, by including purity
parameters, QCD effects and 4-jets processe
Multifractality and its role in anomalous transport in the disordered XXZ spin-chain
The disordered XXZ model is a prototype model of the many-body localization
transition (MBL). Despite numerous studies of this model, the available
numerical evidence of multifractality of its eigenstates is not very conclusive
due severe finite size effects. Moreover it is not clear if similarly to the
case of single-particle physics, multifractal properties of the many-body
eigenstates are related to anomalous transport, which is observed in this
model. In this work, using a state-of-the-art, massively parallel, numerically
exact method, we study systems of up to 24 spins and show that a large fraction
of the delocalized phase flows towards ergodicity in the thermodynamic limit,
while a region immediately preceding the MBL transition appears to be
multifractal in this limit. We discuss the implication of our finding on the
mechanism of subdiffusive transport.Comment: 13 pages, 8 figure
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