1,083 research outputs found
Observation of Aharonov-Bohm conductance oscillations in a graphene ring
No full textWe investigate experimentally transport through ring-shaped devices etched in graphene and observe clear Aharonov-Bohm conductance oscillations. The temperature dependence of the oscillation amplitude indicates that below 1 K, the phase coherence length is comparable to or larger than the size of the ring. An increase in the amplitude is observed at high magnetic field, when the cyclotron diameter becomes comparable to the width of the arms of the ring. By measuring the dependence on gate voltage, we find that the Aharonov-Bohm effect vanishes at the charge neutrality point, and we observe an unexpected linear dependence of the oscillation amplitude on the ring conductance.Kavli Institute of NanoscienceApplied Science
Muerte de amor
No full textEn cierta medida este programa puede ser una extensión de la entrevista concedida al Pentagrama por el director del Teatro Mayor, Ramiro Osorio, pero es inevitable pasar por alto que en este momento está ocurriendo el estreno de Tristán e Isolda de Richard Wagner, que nació el mismo año de Giuseppe Verdi, es decir, 1913, en Leipzig, la ciudad de Johann Sebastian Bach.
Es sin duda la ópera que más repercusión ha tenido en la historia del drama lírico y en la música, porque Wagner llevó la tonalidad a su límite, el Acorde de Tristán es el más famoso de la historia de la música, y han corrido ríos de tinta por cuenta de la audacia wagneriana, que, como lo han consignado los tratadistas de la historia de la música, abrió las puertas a la música moderna.
El Preludio, expone de manera magistral la propuesta armónica de Wagner. Lo escuchan en una interpretación, en vivo, del Festival de Bayreuth 1966, desde luego con la Orquesta del Festival y la dirección de Karl Bohm. Estructura con habilidad extraordinaria, los siete temas, o leitmotivs,(palabra que, por cierto, jamás fue utilizada por Wagner) más importantes de la obra.Conversión utilizando Windows Media Playe
The Aharonov-Bohm effect in topological semiconductor materials analyzed from the Dirac-Weyl equation
No full textfiguras, gráficas, ilustracionesEl presente trabajo aborda dos tópicos centrales: el primero es el estudio de los potenciales en la física desde una perspectiva de revisión de literatura con el fin de intentar encontrar una relación entre el efecto Aharonov-Bohm, la topología del espacio y los potenciales físicos. El segundo es el análisis teórico del grafeno en una estructura semiconductora de punto cuántico, para su estudio se realiza el análisis del hamiltoniano de Dirac-Weyl en coordenadas cilíndricas; en primera instancia se considera el sistema sin presencia de potencial reproduciendo y ampliando los resultados obtenidos por los investigadores Serrano, Avalos y Cabrera en su artículo titulado “Enhancing the energy spectrum of graphene quantum dot with external magnetic and Aharonov-Bohm flux fields”, y posteriormente se propone el análisis de los niveles de energía del sistema al someterlo a una diferencia de potencial V_0. La solución de los niveles de energía y la ecuación de onda se hallan empleando el método fórmula, un método de solución de ecuaciones diferenciales de segundo orden que consiste en determinar coeficientes por medio de la comparación con la ecuación patrón; la fiabilidad y precisión se corrobora al solucionar la función de onda y los niveles de energía con el método WKB y comparar los resultados. Por último, se observa que los niveles de energía en presencia de un potencial V_0 aumentan y disminuyen la separación entre cada nivel, además la presencia del flujo Aharonov-Bohm en el sistema influye en la diferencia de cada nivel de energía. (Texto tomado de la fuente)The present work addresses two central topics: the first is the study of potentials in physics from a literature review perspective in order to try to find a relationship between the Aharonov-Bohm effect, the topology of space and physical potentials. The second is the theoretical analysis of graphene in a semiconductor quantum dot structure. For its study, the Dirac-Weyl Hamiltonian analysis is carried out in cylindrical coordinates; In the first instance, the system without the presence of potential is considered, reproducing and expanding the results obtained by researchers Serrano, Avalos and Cabrera in their article entitled “Enhancing the energy spectrum of graphene quantum dot with external magnetic and Aharonov-Bohm flux fields”, and later, the analysis of the energy levels of the system is proposed by subjecting it to a potential difference V_0. The solution of the energy levels and the wave function are found using the formula method, a method of solving second-order differential equations that consists in determining coefficients by means of comparison with the standard equation; Reliability and accuracy is confirmed by solving the wave function and energy levels with the WKB method and comparing the results. Finally, it is observed that the energy levels in the presence of a potential V_0 increase and the separation between each one decreases, in addition the presence of the Aharonov-Bohm flow in the system influences the difference of each energy level.MaestríaMagister en Ciencias - FísicaMecánica CuánticaMateria Condensad
High order approximation of a tokamak edge plasma transport minimal model with Bohm boundary conditions
No full textInternational audienceTo address the so-called Bohm boundary conditions, generally imposed at the walls that intercept in a tokamak the magnetic field lines, we consider a simple one-dimensional hyperbolic system that constitutes a minimal transport model for ionic density and momentum. We show that as soon as the solution is smooth, a spectrally accurate approximation can be obtained. To this end, we describe a stabilized spectral element method (SEM) and propose a direct imposition of the Bohm boundary condition in an explicit time marching
Ledarskap i banksektorn : En studie i ledarskap och prestation
No full textSammanfattning Datum: 2020-06-08 Nivå: C-uppsats Institution: EST – Ekonomi, Samhälle & Teknik, Mälardalens Högskola. Författare: Sebastian Beyermann (95/08/08), Ida Bohm (95/08/17), Cornelia Petersen (96/03/08) Titel: Ledarskap i banksektorn - En studie i ledarskap och prestation Handledare: Kerstin Nilsson Nyckelord: Ledarskap, prestation, bank, HRM, mål Frågeställningar: Vilka faktorer i sitt ledarskap anser chefer inom banksektorn främja deras medarbetares arbetsprestation? Vilka faktorer i ett ledarskap anser chefer inom banksektorn kan hämma deras medarbetares arbetsprestation? Syfte: Syftet med denna studie är att bidra med förståelse för vilket typ av ledarskap som är gynnsamt med avseende på arbetsprestation inom banksektorn. Metod: Studien är genomförd med en kvalitativ ansats. Insamlingen av primärdata har skett genom semistrukturerade intervjuer. Studiens sekundärdata är baserad på vetenskapligt granskade artiklar inom uppsatsens forskningsämne. Studiens teori, bakgrund samt problemformulering är baserade på både primärdata och sekundärdata. Slutsats: Den transformativa ledarskapsstilen upplevs genomgående som den mest använda och rekommenderade ledarskapsstilen för att främja arbetsprestation. Strategisk resultathantering kan användas som konkurrensfördel och som ett redskap i ledarskap för att främja arbetsprestation. Tydlighet i mål och visionen hos organisationer är faktorer som behöver kommuniceras med tydlig sammankoppling till varje enskild medarbetare för att skapa framgång för organisationen.
THE SHEPHERD SCHOOL PREPARATORY PROGRAM CONCERT LXXXI Saturday, January 24, 2004 2:00 p.m. Lillian H. Duncan Recital Hall
No full textProgram: Tzigane / Maurice Ravel (1875-1937) -- Chanson Triste / Piotr Ilyich Tchaikovsky (1840-1893) -- Concerto in B-flat Major / Luigi Boccherini (1743-1805) -- Concerto in A Minor, Op. 33 / Camille Saint-Saens (1835-1921) -- Divertimento / Joseph Haydn (1732-1809) -- Concerto in E Minor / Edward Elgar (1857-1934) -- Concerto in B Minor / Antonin Dvorak (1841-1904) -- Pezzo Capricioso / Piotr Ilyich Tchaikovsky (1840-1893) -- The Entertainer / Scott Joplin (1867-1917) -- The Clock / Theodor Kullak (1818-1882) -- By the Lake / Angus Morrison (b. 1902) -- Prelude and Fugue in C Minor, B WV 847 / Johann Sebastian Bach (1685-1750) -- Etude No. 3 "La Campanella" / Franz Liszt (1811-1886) -- Minuet in G Major / Johann Sebastian Bach (1685-1750) -- Mosquito Dance, Op. 62 No. 5 / Felix Mendelssohn (1809-1847) -- Air Varie No.14 in G Major / Charles de Beriot (1802-1870) -- Sonatina in G Major, Op.100 / Antonin Dvorak (1841-1904) -- Introduction and Polonaise / Karl Bohm (1844-1920)
Aharonov-Bohm–Type Effect for Vortices in Josephson-Junction Arrays
No full textThe dynamics of a single vortex present in a ring-shaped (Corbino geometry) two-dimensional array of low-capacity Josephson junctions is studied. The vortex is treated as a macroscopic quantum particle, whose energy levels En(Q0) are periodic functions of the externally induced gauge charge Q0 which is enclosed by the vortex, with a period 2e. This Aharonov-Bohm–type effect may manifest itself as a persistent voltage Vs = dE0(Q0)/dQ0 between interior and exterior contacts, or alternatively as Bloch oscillations. The relation with the Aharonov-Casher effect and the possibility for experimental observation are discussed.
Spectral sum rules for the circular Aharonov-Bohm quantum billiard
No full textThis work presents the results of a quantitative investigation of the “sum rule method” recently proposed by the author for calculating low-lying energy levels. The system considered in detail is the circular Aharonov-Bohm quantum billiard recently introduced by Berry and Robnik. Exact, expressions are derived for the spectral zeta function at positiveinteger values as a function of the magnetic flux. Using the zeta function for fixed angular momentum, we observe a very fast convergence to the exact ground state energy (“precocious convergence”)
Nonlinear Bloch wave dynamics in photonic Aharonov–Bohm cages
No full textWe study the properties of nonlinear Bloch waves in a diamond chain waveguide lattice in the presence of a synthetic magnetic flux. In the linear limit, the lattice exhibits a completely flat (wavevector k-independent) band structure, resulting in perfect wave localization, known as Aharonov-Bohm caging. We find that in the presence of nonlinearity, the Bloch waves become sensitive to k, exhibiting bifurcations and instabilities. Performing numerical beam propagation simulations using the tight-binding model, we show how the instabilities can result in either the spontaneous or controlled formation of localized modes, which are immobile and remain pinned in place due to the synthetic magnetic flux. © 2021 Author(s
Spectral Sum Rules for the Circular Aharonov-Bohm Quantum Billiard
No full textThis work presents the results of a quantitative investigation of the "sum rule method" recently proposed by the author for calculating lowlying energy levels. The system considered in detail is the circular Aharonov-Bohm quantum billiard recently introduced by Berry and Robnik. Exact expressions are derived for the spectral zeta function at positive integer values as a function of the magnetic flux. Using the zeta function for fixed angular momentum, we observe a very fast convergence to the exact ground state energy ("precocious convergence"
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