2,094 research outputs found
Dyonic Giant Magnons in CP^3: Strings and Curves at Finite J
This paper studies giant magnons in AdS_4 x CP^3 using both the string
sigma-model and the algebraic curve. We complete the dictionary of solutions by
finding the dyonic generalisation of the CP^1 string solution, which matches
the `small' giant magnon in the algebraic curve, and by pointing out that the
solution recently constructed by the dressing method is the `big' giant magnon.
We then use the curve to compute finite-J corrections to all cases, which for
the non-dyonic cases always match the AFZ result. For the dyonic RP^3 magnon we
recover the S^5 answer, but for the `small' and `big' giant magnons we obtain
new corrections.Comment: 22 pages, 3 figures, 2 tables. v2 adds note on breather solution, and
minor clarification
Initial experiments concerning quantum information processing in rare-earth-ion doped crystals
In this paper initial experiments towards constructing simple quantum gates
in a solid state material are presented. Instead of using specially tailored
materials, the aim is to select a subset of randomly distributed ions in the
material, which have the interaction necessary to control each other and
therefore can be used to do quantum logic operations. The experimental results
demonstrate that part of an inhomogeneously broadened absorption line can be
selected as a qubit and that a subset of ions in the material can control the
resonance frequency of other ions. This opens the way for the construction of
quantum gates in rare-earth-ion doped crystals.Comment: 24 pages, including 12 figure
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Internally Driven Q-learning - Convergence and Generalization Results
We present an approach to solving the reinforcement learning problem in which agents are provided with internal drives against which they evaluate the value of the states according to a similarity function. We extend Q-learning by substituting internally driven values for ad hoc rewards. The resulting algorithm, Internally Driven Q-learning (IDQ-learning), is experimentally proved to convergence to optimality and to generalize well. These results are preliminary yet encouraging: IDQ-learning is more psychologically plausible than Q-learning, and it devolves control and thus autonomy to agents that are otherwise at the mercy of the environment (i.e., of the designer)
(2,0) theory on circle fibrations
We consider (2,0) theory on a manifold M_6 that is a fibration of a spatial
S^1 over some five-dimensional base manifold M_5. Initially, we study the free
(2,0) tensor multiplet which can be described in terms of classical equations
of motion in six dimensions. Given a metric on M_6 the low energy effective
theory obtained through dimensional reduction on the circle is a Maxwell theory
on M_5. The parameters describing the local geometry of the fibration are
interpreted respectively as the metric on M_5, a non-dynamical U(1) gauge field
and the coupling strength of the resulting low energy Maxwell theory. We derive
the general form of the action of the Maxwell theory by integrating the reduced
equations of motion, and consider the symmetries of this theory originating
from the superconformal symmetry in six dimensions. Subsequently, we consider a
non-abelian generalization of the Maxwell theory on M_5. Completing the theory
with Yukawa and phi^4 terms, and suitably modifying the supersymmetry
transformations, we obtain a supersymmetric Yang-Mills theory which includes
terms related to the geometry of the fibration.Comment: 24 pages, v2 References added, typos correcte
Exact and Approximate Formulas for Neutrino Mixing and Oscillations with Non-Standard Interactions
We present, both exactly and approximately, a complete set of mappings
between the vacuum (or fundamental) leptonic mixing parameters and the
effective ones in matter with non-standard neutrino interaction (NSI) effects
included. Within the three-flavor neutrino framework and a constant matter
density profile, a full set of sum rules is established, which enables us to
reconstruct the moduli of the effective leptonic mixing matrix elements, in
terms of the vacuum mixing parameters in order to reproduce the neutrino
oscillation probabilities for future long-baseline experiments. Very compact,
but quite accurate, approximate mappings are obtained based on series
expansions in the neutrino mass hierarchy parameter \eta \equiv \Delta
m^2_{21}/\Delta m^2_{31}, the vacuum leptonic mixing parameter s_{13} \equiv
\sin\theta_{13}, and the NSI parameters \epsilon_{\alpha\beta}. A detailed
numerical analysis about how the NSIs affect the smallest leptonic mixing angle
\theta_{13}, the deviation of the leptonic mixing angle \theta_{23} from its
maximal mixing value, and the transition probabilities useful for future
experiments are performed using our analytical results.Comment: 29 pages, 8 figures, final version published in J. High Energy Phy
Method of extending hyperfine coherence times in Pr^3+:Y_2SiO_5
In this letter we present a method for increasing the coherence time of
praseodymium hyperfine ground state transitions in Pr^3+:Y_2SiO_5 by the
application of a specific external magnetic field. The magnitude and angle of
the external field is applied such that the Zeeman splitting of a hyperfine
transition is at a critical point in three dimensions, making the first order
Zeeman shift vanishingly small for the transition. This reduces the influence
of the magnetic interactions between the praseodymium ions and the spins in the
host lattice on the transition frequency. Using this method a phase memory time
of 82ms was observed, a value two orders of magnitude greater than previously
reported. It is shown that the residual dephasing is amenable quantum error
correction
Coherent transient data-rate conversion and data transformation
Temporal compressions of optical pulses and pulse trains have been performed by the photon-echo process in Tm-doped YAG at 793 nm. Single-pulse temporal compression by almost a. factor of 500 from 10 mu s to 22 ns and pulse train compression by a factor of 14 from 5 mu s to 350 ns with a high-speed frequency-tunable external-cavity diode laser are demonstrated. It is suspected that significantly higher compression could be obtained by improved control of the laser frequency and laser frequency chirps. Theoretically, Tm-doped YAG should be capable of compressing single pulses by almost a factor of 10(7)
Finite-gap equations for strings on AdS_3 x S^3 x T^4 with mixed 3-form flux
We study superstrings on AdS_3 x S^3 x T^4 supported by a combination of
Ramond-Ramond and Neveu-Schwarz-Neveu-Schwarz three form fluxes, and construct
a set of finite-gap equations that describe the classical string spectrum.
Using the recently proposed all-loop S-matrix we write down the all-loop Bethe
ansatz equations for the massive sector. In the thermodynamic limit the Bethe
ansatz reproduces the finite-gap equations. As part of this derivation we
propose expressions for the leading order dressing phases. These phases differ
from the well-known Arutyunov-Frolov-Staudacher phase that appears in the pure
Ramond-Ramond case. We also consider the one-loop quantization of the algebraic
curve and determine the one-loop corrections to the dressing phases. Finally we
consider some classical string solutions including finite size giant magnons
and circular strings.Comment: 44 pages, 3 figures. v2: references and a discussion about
perturbative results adde
A case report on a patient suffering from recurrent vomiting episodes, whose condition improved markedly during pregnancy and breast feeding
BACKGROUND: The normal physiology of the gastrointestinal tract has been only cursorily examined. Consequently, the pathophysiology of disturbances of the gastrointestinal functions is poorly known. Recurrent vomiting is one of many functional conditions for which it is difficult to find an explanation and to treat. In the following a case is described of a patient presenting with recurrent vomiting episodes, whose condition improved spontaneously during pregnancy and breast feeding. CASE PRESENTATION: A woman with recurrent vomiting episodes over several years was examined by esophagogastroduodenoscopy. This showed a non-peristaltic ventricle. Treatment with the procinetic drug cisapride (Prepulsid(®)) improved the peristalsis and reduced the symptoms. During pregnancy and breast feeding, she was free of symptoms, in spite of having discontinued her medication with cisapride (Prepulsid(®)). CONCLUSION: The fact that the patient improved during pregnancy and breast feeding, would seem to indicate the involvement of factors in the physiology of pregnancy and breast feeding that are of importance for gastric motility. This deserves further investigation
Magnetic moments of the low-lying , resonances within the framework of the chiral quark model
The magnetic moments of the low-lying spin-parity ,
resonances, like, for example, ,
, as well as their transition magnetic moments, are
calculated using the chiral quark model. The results found are compared with
those obtained from the nonrelativistic quark model and those of unitary chiral
theories, where some of these states are generated through the dynamics of two
hadron coupled channels and their unitarization
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