The neutrino charge radius is a physical observable

We present a method which allows, at least in principle, the direct extraction of the gauge-invariant and process-independent neutrino charge radius (NCR) from experiments. Under special kinematic conditions, the judicious combination of neutrino and anti-neutrino forward differential cross-sections allows the exclusion of all target-dependent contributions, such as gauge-independent box-graphs, not related to the NCR. We show that the remaining contributions contain universal, renormalization group invariant combinations, such as the electroweak effective charge and the running mixing angle, which must be also separated out. By considering the appropriate number of independent experiments we show that one may systematically eliminate these universal terms, and finally express the NCR entirely in terms of physical cross-sections. Even though the kinematic conditions and the required precision may render the proposed experiments unfeasible, at the conceptual level the analysis presented here allows for the promotion of the NCR into a genuine physical observable.Comment: 34 pages, 5 figure

The effective neutrino charge radius

It is shown that at one-loop order a neutrino charge radius (NCR) may be defined, which is ultraviolet finite, does not depend on the gauge-fixing parameter, nor on properties of the target other than its electric charge. This is accomplished through the systematic decomposition of physical amplitudes into effective self-energies, vertices, and boxes, which separately respect electroweak gauge invariance. In this way the NCR stems solely from an effective proper photon-neutrino one-loop vertex, which satisfies a naive, QED-like Ward identity. The NCR so defined may be extracted from experiment, at least in principle, by expressing a set of experimental electron-neutrino cross-sections in terms of the finite NCR and two additional gauge- and renormalization-group-invariant quantities, corresponding to the electroweak effective charge and mixing angle.Comment: Talk given at EPS2003 - Aachen, Germany, July 2003; 3 pages, no figure

Magnetic polarons in doped 1D antiferromagnetic chain

The structure of magnetic polarons (ferrons) is studied for an 1D antiferromagnetic chain doped by non-magnetic donor impurities. The conduction electrons are assumed to be bound by the impurities. Such a chain can be described as a set of ferrons at the antiferromagnetic background. We found that two types of ferrons can exist in the system. The ground state of the chain corresponds to the ferrons with the sizes of the order of the localization length of the electron near the impurity. The ferrons of the second type produce a more extended distortion of spins in the chain. They are stable within a finite domain of the system parameters and can be treated as excitations above the ground state. The ferrons in the excited states can appear in pairs only. The energy of the excited states decreases with the growth in density of impurities. This can be interpreted as a manifestation of an attractive interaction between ferrons.Comment: 6 pages, 5 figures, RevTex4, submitted to PR

Effects of Commission Errors during Noncontingent Reinforcement

Noncontingent reinforcement (NCR) is a behavioral treatment in which a reinforcer is provided at set intervals independently of responding. Although NCR is commonly used, effects of inconsistent implementation (i.e., implementation with integrity failures) during NCR were previously unknown. The current study included six participants, but full-integrity NCR suppressed problem behavior for only three participants. Thus, we evaluated effects of one kind of integrity failure, reinforcement of problem behavior, on NCR outcomes for three children who engaged in inappropriate vocalizations maintained by access to tangible items. Effects of commission errors were idiosyncratic across participants

Refining Noncontingent Reinforcement Treatments Using Behavioral Momentum Theory

One of the most effective and commonly prescribed treatments for children with autism and/or an intellectual disability who engage in severe destructive behavior is called noncontingent reinforcement (NCR). During NCR, the consequence that previously reinforced destructive behavior is delivered on a time-based schedule, independent of destructive behavior, and the contingency between destructive behavior and its reinforcer is discontinued (operant extinction; EXT). Conceptual and quantitative derivations of behavioral momentum theory (BMT) suggest that certain aspects of NCR may inadvertently promote persistence of destructive behavior, thereby prolonging the treatment process. Guided by Shahan and Sweeney’s (2011) model of resurgence based on BMT, this dissertation evaluated two refinements to NCR designed to reduce behavioral persistence during treatment and mitigate response resurgence following NCR when all reinforcement was withdrawn. In Experiment 1, we evaluated a procedure designed to increase the saliency of the change from contingent reinforcement to NCR by altering a reinforcer parameter related to contingency discriminability, which BMT predicts will lead to faster reductions in target responding and decrease the likelihood of resurgence. Behavioral momentum theory also predicts that implementing NCR without EXT (as is commonly done for destructive behavior maintained by sensory reinforcers) increases the likelihood of resurgence. Therefore, in Experiment 2, we compared levels of resurgence when NCR was implemented with and without EXT. Results suggest that the proposed refinements are effective, to varying degrees, at reducing behavioral persistence during NCR and mitigating response resurgence. Findings are discussed within a translational research framework and broader context of strategies used to mitigate treatment relapse for severe destructive behavior

Topological Non--connectivity Threshold in long-range spin systems

We demonstrate the existence of a topological disconnection threshold, recently found in Ref. \cite{JSP}, for generic $1-d$ anisotropic Heisenberg models interacting with an inter--particle potential $R^{-\alpha}$ when $0<\alpha < 1$ (here $R$ is the distance among spins). We also show that if $\alpha$ is greater than the embedding dimension $d$ then the ratio between the disconnected energy region and the total energy region goes to zero when the number of spins becomes very large. On the other hand, numerical simulations in $d=2,3$ for the long-range case $\alpha < d$ support the conclusion that such a ratio remains finite for large $N$ values. The disconnection threshold can thus be thought as a distinctive property of anisotropic long-range interacting systems.Comment: submitted to PR

Supersolidity in quantum films adsorbed on graphene and graphite

Using quantum Monte Carlo we have studied the superfluid density of the first layer of $^4$He and H$_2$ adsorbed on graphene and graphite. Our main focus has been on the equilibrium ground state of the system, which corresponds to a registered $\sqrt3 \times \sqrt3$ phase. The perfect solid phase of H$_2$ shows no superfluid signal whereas $^4$He has a finite but small superfluid fraction (0.67%). The introduction of vacancies in the crystal makes the superfluidity increase, showing values as large as 14% in $^4$He without destroying the spatial solid order.Comment: 5 pages, accepted for publication in PR

Optical DPSK with generalized phase noise model and narrowband reception

Caption title.Includes bibliographical references.Supported by the NSF. NCR-8802991 NCR-9206379 Supported by DARPA. F19628-90-C-0002 Supported by the ARO. DAAL03-92-G-0115Murat AzizoÄlu, Pierre A. Humblet