4,639 research outputs found
Null Half-Supersymmetric Solutions in Five-Dimensional Supergravity
We classify half-supersymmetric solutions of gauged N=2, D=5 supergravity
coupled to an arbitrary number of abelian vector multiplets for which all of
the Killing spinors generate null Killing vectors. We show that there are four
classes of solutions, and in each class we find the metric, scalars and gauge
field strengths. When the scalar manifold is symmetric, the solutions
correspond to a class of local near horizon geometries recently found by
Kunduri and Lucietti.Comment: 46 pages, typos corrected and reference added. Section 7.1 has been
added: it is shown that the solutions found here correspond to a class of
solutions found in arXiv:0708.3695. Uses JHEP3.cl
Information embedding meets distributed control
We consider the problem of information embedding where the encoder modifies a
white Gaussian host signal in a power-constrained manner to encode the message,
and the decoder recovers both the embedded message and the modified host
signal. This extends the recent work of Sumszyk and Steinberg to the
continuous-alphabet Gaussian setting. We show that a dirty-paper-coding based
strategy achieves the optimal rate for perfect recovery of the modified host
and the message. We also provide bounds for the extension wherein the modified
host signal is recovered only to within a specified distortion. When
specialized to the zero-rate case, our results provide the tightest known lower
bounds on the asymptotic costs for the vector version of a famous open problem
in distributed control -- the Witsenhausen counterexample. Using this bound, we
characterize the asymptotically optimal costs for the vector Witsenhausen
problem numerically to within a factor of 1.3 for all problem parameters,
improving on the earlier best known bound of 2.Comment: 19 pages, 7 figures. Presented at ITW'10. Submitted to IEEE
Transactions on Information Theor
Policy Initiatives by the Government of India to Accelerate the Growth of Installed Nuclear Power Capacity in the Coming Years
AbstractWhen examined from the point of view of the size of its population and economy, India is not well endowed with energy resources. Studies done by the Department of Atomic Energy indicate that even after exploiting full potential of every available source of energy including nuclear energy, India needs to continue to import energy resources. In this backdrop, an initiative was launched by Government of India to open up international civil nuclear commerce so as to enable India to access natural uranium from international market and to set up nuclear reactors in technical cooperation with other countries. The paper provides details of what has been done so far, ongoing steps and likely growth scenario for nuclear installed capacity in the country
Measurement of an integral of a classical field with a single quantum particle
A method for measuring an integral of a classical field via local interaction
of a single quantum particle in a superposition of 2^N states is presented. The
method is as efficient as a quantum method with N qubits passing through the
field one at a time and it is exponentially better than any known classical
method that uses N bits passing through the field one at a time. A related
method for searching a string with a quantum particle is proposed.Comment: 3 page
Query complexity for searching multiple marked states from an unsorted database
An important and usual problem is to search all states we want from a
database with a large number of states. In such, recall is vital. Grover's
original quantum search algorithm has been generalized to the case of multiple
solutions, but no one has calculated the query complexity in this case. We will
use a generalized algorithm with higher precision to solve such a search
problem that we should find all marked states and show that the practical query
complexity increases with the number of marked states. In the end we will
introduce an algorithm for the problem on a ``duality computer'' and show its
advantage over other algorithms.Comment: 4 pages,4 figures,twocolum
Noise in Grover's Quantum Search Algorithm
Grover's quantum algorithm improves any classical search algorithm. We show
how random Gaussian noise at each step of the algorithm can be modelled easily
because of the exact recursion formulas available for computing the quantum
amplitude in Grover's algorithm. We study the algorithm's intrinsic robustness
when no quantum correction codes are used, and evaluate how much noise the
algorithm can bear with, in terms of the size of the phone book and a desired
probability of finding the correct result. The algorithm loses efficiency when
noise is added, but does not slow down. We also study the maximal noise under
which the iterated quantum algorithm is just as slow as the classical
algorithm. In all cases, the width of the allowed noise scales with the size of
the phone book as N^-2/3.Comment: 17 pages, 2 eps figures. Revised version. To be published in PRA,
December 199
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Situating multimodal learning analytics
The digital age has introduced a host of new challenges and opportunities for the learning sciences community. These challenges and opportunities are particularly abundant in multimodal learning analytics (MMLA), a research methodology that aims to extend work from Educational Data Mining (EDM) and Learning Analytics (LA) to multimodal learning environments by treating multimodal data. Recognizing the short-term opportunities and longterm challenges will help develop proof cases and identify grand challenges that will help propel the field forward. To support the field's growth, we use this paper to describe several ways that MMLA can potentially advance learning sciences research and touch upon key challenges that researchers who utilize MMLA have encountered over the past few years
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