Exact calculation of current correlations and admittance in the fractional quantum Hall regime

In this work, we focus on the finite frequency current-current correlations between edge states in a fractional quantum Hall two dimensional gas and on their relations to the quantum admittance. Using a refermionization method, we calculate these quantities within the same framework. Our results apply whatever the values of backscattering amplitude, frequency, voltage and temperature, allowing us to reach different regimes. Auto-correlations and cross-correlations exhibit distinct frequency dependencies that we discuss in detail.Comment: 4 pages, 7 figure

Finite-frequency noise in a non-interacting quantum dot

We calculate the non-symmetrized finite-frequency NS-FF noise for a single-level quantum dot connected to reservoirs in the spinless non-interacting case. The calculations are performed within the framework of the Keldysh Green's function formalism in the wide band approximation limit. We establish the general formula for NS-FF noise for any values of temperature, frequency and bias voltage. The electron transfer processes from one to the other reservoir act via the transmission amplitude and transmission coefficient depending on the energy. By taking the symmetrized version of this expression, we show that our result coincides with the expression of the finite frequency noise obtained by B\"uttiker using the scattering theory. We also give the explicit analytical expression for the NS-FF noise in the zero temperature limit. By performing numerical calculations, we finally discuss the evolution of the NS-FF noise spectrum when varying temperature, dot energy level, and coupling strength to the reservoirs, revealing a large variety of behaviors with different symmetry properties.Comment: Proceeding of the UPON 2015 conferenc

Crisis Management: A Historical and Conceptual Approach for a Better Understanding of Today’s Crises

We argue that the basic and contemporary concepts related to crisis management, especially in the communication field, share some similarities with what was practiced in ancient civilizations such as the importance of direct contact between the leadership and the public. Other similarities include the accurate diagnosis of the real causes of the crisis, the forbiddance of the dissemination of false news and the reassurance of the public opinion that there is a solution to the crisis, a sound management decision, and a good plan for its implementation. We link the past time crises to the contemporary era, providing a comparison framework. The history of crisis tends to show us that the study of crisis management cannot be linked to a specific civilization or era, especially when humanity had witnessed multiple and complex environmental, political, economic, and military crisis. Moreover, some of the problems and complex issues in the modern era are rooted in history. Thus, many geopolitical crises nowadays are the result of old causes. The study of crisis management from an academic point of view should be a multifaceted analysis, including a historical, a cultural, and an anthropological one, which determines the course of evolution and consequences of the crisis

Density of states of interacting quantum wires with impurities: A Dyson equation approach

International audienceWe calculate the density of states for an interacting quantum wire in the presence of two impurities of arbitrary potential strength. To perform this calculation, we describe the Coulomb interactions in the wire within the Tomonaga-Luttinger liquid theory. After establishing and solving the Dyson equation for the fermionic retarded Green's functions, we study how the profile of the local density of states is affected by the interactions in the entire range of impurity potentials. Same as in the non-interacting case, when increasing the impurity strength, the central part of the wire becomes more and more disconnected from the semi-infinite leads, and discrete localized states begin to form; the width and the periodicity of the corresponding peaks in the spectrum depends on the interaction strength. As expected from the Luttinger liquid theory, impurities also induce a reduction of the local density of states at small energies. Two other important aspects are highlighted: the appearance of an extra modulation in the density of states at nonzero Fermi momentum when interactions are present, and the fact that forward scattering must be taken into account in order to recover the Coulomb-blockade regime for strong impurities

Random access techniques for satellite communications

The effective coverage of satellites and the technology behind have motivated many actors to develop efficient communications for Internet access, television and telephony. For a long time, reservation resources of Demand Assignment Multiple Access (DAMA) techniques have been largely deployed in the return link of satellite communications, occupying most of the frequency bandwidth. However, these resources cannot follow the technological growth with big users communities in applications like the Internet of Things and Machine to Machine communications. Especially because the Round Trip Time is significant in addition to a potential underuse of the resources. Thus, access protocols based on ALOHA took over a big part of the Random Access (RA) research area and have considerably evolved lately. CRDSA have particularly put its fingerprint in this domain, which inspired many different techniques. In this context, a complementary method, called MARSALA comes to unlock CRDSA when packets can no longer be retrieved. This actually involves a correlation complexity related to packet localization which is necessary for replicas combinations that results in a potentially higher signal power. Accordingly, the main goal of this PhD research is to seek for effective and less complex alternatives. More precisely, the core challenge focuses on the way to manage multi-user transmissions and solve interference at reception, with the smallest complexity. In addition, the loop phenomenon which occur when multiple users transmit their packets at the same positions is tackled as it creates an error floor at the packet loss ratio performance. Synchronous and asynchronous solutions are proposed in this thesis, mainly based on providing the transmitter and the receiver with a shared prior information that could help reduce the complexity, mitigate the loop phenomenon and enhance the system performance. An in-depth description and analysis of the proposed techniques are presented in this dissertation

Natural enemies emerged from Thaumetopoea pityocampa (Denis & Sciffermüller) (Lepidoptera Notodontidae) pupae in Southern Italy.

Observation made over a 4-year period in pinewoods of Apulia Region (South Italy) on Thaumetopoea pityocampa (Denis Sciffermüller) (Lepidoptera: Notodontidae) prepupae and pupae, indicated the following natural enemies complex: Hexamermis sp. (Nematoda: Mermithidae), Phryxe caudata (Diptera: Tachinidae), Villa brunnea and Hemipenthes velutina (Diptera: Bombyliidae), Conomorium pityocampae (Hymenoptera: Pteromalidae), Coelichneumon rudis and Cryptus sp. (Hymenoptera: Ichneumonidae), Beauveria bassiana and Isaria farinosa (formerly Paecylomices farinosus) (Ascomycota: Hypocreales). The moths and the parasitoid species emerged sequentially and, although these natural enemies show irregular distribution, they together controlled up to 60% of T. pityocampa pupae. Ecological implications of such parasitism are being discussed

Structure des communautés d’ennemis naturels de Thaumetopoea pityocampa Denis & Schiffermüller (Lep., Thaumetopoeidae) sur pin d’Alep en Algérie

THE NATURAL ENEMIES COMMUNITIES STRUCTURE OF THAUMETOPOEA PITYOCAMPA DENIS SCHIFFERMÜLLER (LEP., THAUMETOPOEIDAE) ON PINUS HALEPENSIS IN THE SUBSAHARAN ALGERIA The host plants of the pine processionary caterpillars, Thaumetopoea pityocampa (Den. and Schiff.) (Lep., Thaumetopoeidae), are the Pinus and Cedrus. This study was carried out in the forest of Pinus halepensis Mill. in the subsaharian region where this insect pest was in a permanent presence. The structure of the natural enemies complex of this insect is analysed. Data on incidence of the various parasitoïds and predatory species are estimed. It appears that the majority of the entomophagous species attacking the pine processionary caterpillars were met in the studied area. It seems that the specific parasitoïds of different development stages, i.e. Baryscapus servadeii for eggs, Phryxe caudata, Erigorgus, femorator for the caterpillars, and, Villa brunnea for the pupae have a hight incidence in the regulation of the pine processionary caterpillars populations. It can exceed 80 % in certain pupae sites. However, in the subsaharian pine forest, predation by Scolopender was observed against the caterpillars in the pupal sites and hedgehog attacking the adults. These observations were not recorded in the other localities in the Mediterranean basin. Key words: Lepidoptera, insect forest pest, parasitism, incidence, Mediterranean basin

Structures in Mo-Ru-Si system by powder and anomal X-ray diffraction

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One-channel conductor coupled to a quantum of resistance: exact ac conductance and finite-frequency noise

We consider a one-channel coherent conductor with a good transmission embedded into an ohmic environment whose impedance is equal to the quantum of resistance R_q=h/e^2 below the RC frequency. This choice is motivated by the mapping of this problem to a Tomonaga-Luttinger liquid with one impurity whose interaction parameter corresponds to the specific value K=1/2, allowing for a refermionization procedure. The "new" fermions have an energy-dependent transmission amplitude which incorporates the strong correlation effects and yields the exact dc current and zero-frequency noise through expressions similar to those of the scattering approach. We recall and discuss these results for our present purpose. Then we compute, for the first time, the finite-frequency differential conductance and the finite-frequency non-symmetrized noise. Contrary to intuitive expectation, both cannot be expressed within the scattering approach for the new fermions, even though they are still determined by the transmission amplitude. Even more, the finite-frequency conductance obeys an exact relation in terms of the dc current which is similar to that derived perturbatively with respect to weak tunneling within the Tien-Gordon theory, and extended recently to arbitrary strongly interacting systems coupled eventually to an environment or/and with a fractional charge. We also show that the emission excess noise vanishes exactly above eV, even though the underlying Tomonaga-Luttinger liquid model corresponds to a many-body correlated system. Our results apply for all ranges of temperature, voltages and frequencies below the RC frequency, and they allow to explore fully the quantum regime.Comment: 15 pages, 11 figure