Active Topology Inference using Network Coding

Our goal is to infer the topology of a network when (i) we can send probes between sources and receivers at the edge of the network and (ii) intermediate nodes can perform simple network coding operations, i.e., additions. Our key intuition is that network coding introduces topology-dependent correlation in the observations at the receivers, which can be exploited to infer the topology. For undirected tree topologies, we design hierarchical clustering algorithms, building on our prior work. For directed acyclic graphs (DAGs), first we decompose the topology into a number of two-source, two-receiver (2-by-2) subnetwork components and then we merge these components to reconstruct the topology. Our approach for DAGs builds on prior work on tomography, and improves upon it by employing network coding to accurately distinguish among all different 2-by-2 components. We evaluate our algorithms through simulation of a number of realistic topologies and compare them to active tomographic techniques without network coding. We also make connections between our approach and alternatives, including passive inference, traceroute, and packet marking

Towards the complete N=2 superfield Born-Infeld action with partially broken N=4 supersymmetry

We propose a systematic way of constructing $N=2, d=4$ superfield Born-Infeld action with a second nonlinearly realized N=2 supersymmetry. The latter, together with the manifest N=2 supersymmetry, form a central-charge extended $N=4, d=4$ supersymmetry. We embed the Goldstone-Maxwell N=2 multiplet into an infinite-dimensional off-shell supermultiplet of this N=4 supersymmetry and impose an infinite set of covariant constraints which eliminate all extra N=2 superfields through the Goldstone-Maxwell one. The Born-Infeld superfield Lagrangian density is one of these composite superfields. The constraints can be solved by iterations to any order in the fields. We present the sought N=2 Born-Infeld action up to the 10th order. It encompasses the action found earlier by Kuzenko and Theisen to the 8th order from a self-duality requirement. This is a strong indication that the complete N=2 Born-Infeld action with partially broken N=4 supersymmetry is also self-dual.Comment: 12 pages, LaTeX, typos corrected, version to appear in Phys. Rev.

Superconformal mechanics and nonlinear supersymmetry

We show that a simple change of the classical boson-fermion coupling constant, $2\alpha \to 2\alpha n$, $n\in \N$, in the superconformal mechanics model gives rise to a radical change of a symmetry: the modified classical and quantum systems are characterized by the nonlinear superconformal symmetry. It is generated by the four bosonic integrals which form the so(1,2) x u(1) subalgebra, and by the 2(n+1) fermionic integrals constituting the two spin-n/2 so(1,2)-representations and anticommuting for the order n polynomials of the even generators. We find that the modified quantum system with an integer value of the parameter $\alpha$ is described simultaneously by the two nonlinear superconformal symmetries of the orders relatively shifted in odd number. For the original quantum model with $|\alpha|=p$, $p\in \N$, this means the presence of the order 2p nonlinear superconformal symmetry in addition to the osp(2|2) supersymmetry.Comment: 16 pages; misprints corrected, note and ref added, to appear in JHE

Leading-Order Actions of Goldstino Fields

This paper starts with a self-contained discussion of the so-called Akulov-Volkov action S_AV, which is traditionally taken to be the leading-order action of Goldstino field. Explicit expressions for S_AV and its chiral version S_AV^ch are presented. We then turn to the issue on how these actions are related to the leading-order action S_NL proposed in the newly proposed constrained superfield formalism. We show that S_NL may yield S_AV/S_AV^ch or a totally different action S_KS, depending on how the auxiliary field in the former is integrated out. However, S_KS and S_AV/S_AV^ch always yield the same S-matrix elements, as one would have expected from general considerations in quantum field theory.Comment: Minor changes, version to appear in European Physical Journal

Facility development for a combined cancer therapy

The system for local hyperthermia of cancers was simulated. This system is based on independently phased dipoles with frequency 150 MHz. The electromagnetic field distributions are calculated in cut of tissue-equivalent phantom. It was shown that the electromagnetic field can be focused in desirable volume by means of independent vary of amplitude and phase of each dipole. The advantages of combined therapy are discussed for common using of hyperthermia with chemotherapy, radiation therapy or surgery.Проведено моделирование работы системы для локальной гипертермии онкологических заболеваний на основе системы независимо фазируемых дипольных излучателей, работающих на частоте 150 МГц. Получены картины распределения электрических полей в сечении облучаемого образца (тканеэквивалентного фантома). Показана возможность фокусировки электромагнитного поля в необходимом объеме за счет независимого изменения фазы и амплитуды излучения каждого из диполей. Рассмотрены перспективы комбинированного использования гипертермии и химической или лучевой терапии и хирургии.Проведено моделювання роботи системи для локальної гіпертермії онкологічних захворювань на основі системи незалежно фазіруємих дипольних випромінювачів, що працюють на частоті 150 МГц. Отримано картини розподілу електричних полів у перерізі опромінюваного зразка (тканееквівалентного фантома). Показана можливість фокусування електромагнітного поля в необхідному об’ємі за рахунок незалежної зміни фази і амплітуди випромінювання кожного з диполів. Розглянуто перспективи комбінованого використання гіпертермії та хімічної або променевої терапії та хірургії

Goldstone multiplet for partially broken superconformal symmetry

The bosonic parts of D3-brane actions in AdS(5) backgrounds are known to have symmetries which are field-dependent extensions of conformal transformations of the worldvolume coordinates. Using the coset space SU(2,2|1)/SO(4,1), we apply the method of nonlinear realizations to construct a four-dimensional N = 1 off-shell supersymmetric action which has a generalized field-dependent superconformal invariance. The Goldstone fields for broken scale, chiral and S-supersymmetry transformations form a chiral supermultiplet.Comment: 10 pages, latex, no figures. References and clarifying Comments added, a more general expression for supermetric (28) give

43. Neoadjuvant radiotherapy of epidermiod lung carcinoma patients under short term hypoxia condition

Main method of treating the epidermoid lung carcinoma patients is a surgery which gives a 5-year survival of 53–70% of patients with 1 and 2 stage of disease. However, if metastases in lymphatic nodes of mediastinum are present then number of patients surviving this period considerably decreases. To increase surgery effectiveness one seeks the combined therapy methods using, in particular, neoadjuvant radiotherapy. We have studied such a therapy method which is to be applied during the pre-operative period of hypoxiradiotherapy. Date of 237 epidermoid lung carcinoma patients has been analyzed, mainly for the 3-d stage of disease: 1-st group of 123 patients was given a surgery treatment, the second one, of 114 patients, received an additional intensive pre-surgery radiation (5 Gy daily, 20 Gy) under condition of a short term hypoxya of a short term hypoxya caused by a gas mixture of 10% of oxygen and 90% of nitrogen. Surgeries were carried out during the first 3 days after the completing the radiation treatment. Mechanical conditions of the surgery procedure, blood losses and after surgery complications were similar in both cases. The number of cases of general radiation reactions decreased 3 times, all the cases being limited to the 1 and 2 degrees on the RTOG scale. After analysis of deferent factors, which define the result of treatment, significance the most reliable were the size of primary lesion and presence of mediastinum lymphatic nodes metastasis. Was shown rising of 3-year survival rate after combined treatment vs. operative treatment only

Properties of hyperkahler manifolds and their twistor spaces

We describe the relation between supersymmetric sigma-models on hyperkahler manifolds, projective superspace, and twistor space. We review the essential aspects and present a coherent picture with a number of new results.Comment: 26 pages. v2: Sign mistakes corrected; Kahler potential explicitly calculated in example; references added. v3: Published version--several small clarifications per referee's reques

Kohn Anomalies in Superconductors

I present the detailed behavior of phonon dispersion curves near momenta which span the electronic Fermi sea in a superconductor. I demonstrate that an anomaly, similar to the metallic Kohn anomaly, exists in a superconductor's dispersion curves when the frequency of the phonon spanning the Fermi sea exceeds twice the superconducting energy gap. This anomaly occurs at approximately the same momentum but is {\it stronger} than the normal-state Kohn anomaly. It also survives at finite temperature, unlike the metallic anomaly. Determination of Fermi surface diameters from the location of these anomalies, therefore, may be more successful in the superconducting phase than in the normal state. However, the superconductor's anomaly fades rapidly with increased phonon frequency and becomes unobservable when the phonon frequency greatly exceeds the gap. This constraint makes these anomalies useful only in high-temperature superconductors such as $\rm La_{1.85}Sr_{.15}CuO_4$.Comment: 18 pages (revtex) + 11 figures (upon request), NSF-ITP-93-7

Nonlinear Realization of N=2 Superconformal Symmetry and Brane Effective Actions

Due to the incompatibility of the nonlinear realization of superconformal symmetry and dilatation symmetry with the dilaton as the compensator field, in the present paper it shows an alternative mechanism of spontaneous breaking the N=2 superconformal symmetry to the N=0 case. By using the approach of nonlinear transformations it is found that it leads to a space-filling brane theory with Weyl scale W(1,3) symmetry. The dynamics of the resulting Weyl scale invariant brane, along with that of other Nambu-Goldstone fields, is derived in terms of the building blocks of the vierbein and the covariant derivative from the Maurer-Cartan oneforms. A general coupling of the matter fields localized on the brane world volume to these NG fields is also constructed.Comment: 22 pages, more references and comments are adde