1,015 research outputs found
Scaling up qualitative data: with Professor Ken Benoit
No full textProfessor Benoit is the Principal Investigator in an ERC funded project QUANTESS developing innovative methods for the quantitative analysis of textual data in the social sciences. He is the co-author with Paul Nulty of the R software package for text analysis “quanteda”, and working on a book Quantitative Text Analysis Using R covering methods for managing, processing, and analysing textual data using the R programming language. He has taught quantitative text analysis extensively and has published research in this area targeting both methodology and political science applications
SEQUENTIAL MAGNETOTUNNELING IN A VERTICAL QUANTUM DOT TUNED AT THE CROSSING TO HIGHER SPIN STATES
No full textWe have calculated the Linear magnetoconductance across a vertical parabolic quantum dot with a magnetic field in the direction of the current. Gate voltage and magnetic field an tuned at the degeneracy point between the occupancies N=2 and N=3, close to the singlet-triplet transition for N=2. We find that the conductance is enhanced prior to the transition by nearby crossings of the levels of the three-particle dot. Immediately after it is depressed by roughly 1/3, as long as the total spin S of the three-electron ground state doesn't change from S=1/2 to S=3/2, due to spin selection rule. At low temperature this dip is very sharp, but the peak is recovered by increasing the temperature
Thesium philosophicarum fasciculus
No full textquem ... praeside ... Io. Friderico Benoit ... publicè tutabitur Ioh. Rodolphus Kochius, HBernas, phil. stud. author & respondens, ad diem 5. Martii ...Diss. Hohe Schule Bern, 171
Far infrared absorption of noncenter-of-mass modes and an optical sum rule in a few-electron quantum dot with Rashba spin-orbit coupling
No full textSpin-orbit interaction in a quantum dot couples far-infrared radiation to noncenter-of-mass excitation modes, even for parabolic confinement and dipole approximation. The intensities of the absorption peaks satisfy the optical sum rule, giving direct information on the total number of electrons inside the dot. In the case of a circularly polarized radiation, the sum rule is insensitive to the strength of a Rashba spin-orbit coupling due to an electric field orthogonal to the dot plane, but not to other sources of spin-orbit interaction, thus allowing one to discriminate between the two
KONDO GROUND STATE IN A QUANTUM DOT WITH AN EVEN NUMBER OF ELECTRONS IN A MAGNETIC FIELD
No full textInternational audienceKondo conduction has been observed in a quantum dot with an even number of electrons at the triplet-singlet degeneracy point produced by applying a small magnetic field B orthogonal to the dot plane. At a much larger field B similar toB*, orbital effects induce the reversed transition from the singlet to the triplet state. We study the newly proposed Kondo behavior at this point. Here the Zeeman spin splitting cannot be neglected, which changes the nature of the Kondo coupling. On the grounds of exact diagonalization results in a dot with cylindrical symmetry, we show that, at odds with what happens at the other crossing point, close to B*, orbital and spin degrees of freedom are "locked together," so that the Kondo coupling involves a fictitious spin 1/2 only, which is fully compensated for by conduction electrons under suitable conditions. In this sense, spin at the dot is fractionalized. We derive the scaling equation of the system by means of a nonperturbative variational approach. The approach is extended to the B not equal B* case and the residual magnetization on the dot is discussed
SPIN EXCITON IN A QUANTUM DOT WITH SPIN-ORBIT COUPLING AT HIGH MAGNETIC FIELDS
No full textCoulomb interactions of few (N) electrons confined in a disk-shaped quantum dot, with a large magnetic field B=B-* applied in the z direction (orthogonal to the dot), produce a fully spin-polarized ground state. We numerically study the splitting of the levels corresponding to the multiplet of total spin S=N/2 (each labeled by a different total angular momentum J(z)) in the presence of an electric field parallel to B, coupled to S by a Rashba term. We find that the first excited state is a spin exciton with a reversed spin at the origin. This is reminiscent of the quantum Hall ferromagnet at filling one, which has the skyrmionlike state as its first excited state. The spin-exciton level can be tuned with the electric field and infrared radiation can provide energy and angular momentum to excite it
Fables de La Fontaine: Une Anthologie proposée par Benoit Marchon
No full textHere are forty-three fables presented by an artist I have enjoyed twice elsewhere. The book's unusual shape (6½ x 10¾) is the first clue that it is going to present traditional material in a fresh way. Almost every presentation involves two pages and clever positioning of a few key images. GA (10-11) presents an ant with a sack of grain on his back marching across the page above a grasshopper moving upwards with a guitar on his back: character, load, and direction are all different. FC presents a cheese with its owner's name struck through and changed from Corbeau to Renard (12-13). WS shows a stork with a scissors for a head beside an x-ray of a wolf's digestive tract with the bone lodged down the throat (22-23). The spilt milk of MM is blotting out drawings of hens, pig, and cow (30-31). The surreal style fits the approach perfectly. Sometimes I have no idea why an object is presented the way Jarrie presents it; other times it is perfect. The bull in OF holds the frog by a tether as though the latter were a helium-filled balloon (32-33). Maybe best of all is The Rat and the Elephant (50-51). The elephant is segmented to make room for the text. Between the elephant's legs, mostly hidden from us, a cat reaches out a paw for the minuscule rat under the elephant's big belly. For sheer fun, try The Lion Defeated by a Man (78-79). The book has a place-holding ribbon, a short life of both La Fontaine and of Jarrie, and a helpful glossary of unusual language in the fables. This book fulfills its rear cover's promise of a fresh entry into a fabulous zoological park. Bravo, Jarrie!This is a hardbound book (hard cover)Language note: FrenchJean de La Fontaine; Benoit Marcho
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