484 research outputs found
Spin-orbit coupled Bose-Einstein condensates in a double well
No full textWe study the quantum dynamics of spin-orbit (SO) coupled Bose-Einstein condensates (BECs) in a double-well potential inspired by the recent experiment developed by NIST group. We focus on the regime where the number of atoms is very large and perform a two-mode approximation. An analytical solution of the two-site Bose-Hubbard-like Hamiltonian is found for weak nonlinear interactions by a rotating wave approximation (RWA). The quantum dynamics of several observables, ranging from the population and pseudospin imbalance, to the atomic and spin current are explicitly computed. We show a spin Josephson effect which could be detected in experiments and employed in realistic devices
The development of the concept of exchange forces in the 1930s: close encounters between Europe and Japan and the birth of nuclear theory
No full textThe onset and the development of the concept of exchange force in quantum physics are historically reconstructed, starting from Heisenberg’s seminal contributions in 1926 and going through the great developments in nuclear physics, which allowed the emergence of the idea of force mediating virtual quanta. Although most of such work was performed in Europe, the last and decisive effort in this long path was carried out by Japanese scientists in the 1930s. This is the main focus of the present work, which retraces the achievements of Yukawa and Tomonaga, whose results and mutual interactions are carefully analyzed and related to those of European physicists
A spasso con Feynman per le scintillanti strade dell'elettromagnetismo classico
No full textL’originale e poliedrico approccio di Richard P. Feynman all’elettro- magnetismo classico viene qui presentato nella sua generalita`, ripercorrendo l’in- tero percorso storico, dalla iniziale “teoria dell’assorbitore” all’approccio origina- le e poco noto delineato in appunti manoscritti del 1963 e sviluppato poi nelle Hughes Lectures del 1967-68. Alcune considerazioni che emergono da tale ap- proccio, particolarmente stimolanti, riguardo il pensiero di Feynman sulla natura dell’elettromagnetismo e, piu` in generale, delle interazioni fondamentali, vengono inoltre offerte al lettore interessato
Measuring a Mass: The Puzzling History of an Elusive Particle
No full textSince Pauli’s hypothesis of their existence in 1930, neutrinos never ceased to bring into play novel ideas and to add new pieces of physics in the whole picture of fundamental interactions. They are only weakly interacting and, at odds with Standard Model’s predictions, have a mass less than one millionth of the electron mass, which makes the investigation of their properties very challenging. The issue of the measurement of neutrino’s rest mass gained a wider and wider consensus since its discovery through neutrino oscillations in 1998. Various neutrino sources are available for experiments, ranging from nuclear collisions of cosmic rays in the Earth atmosphere and supernova explosions to neutrino beams produced by accelerators and power reactors. These suggest different approaches to the experimental detection and measurement of the absolute value of the neutrino mass. In this paper, we retrace the intriguing story of this endeavor, focusing mainly on direct mass determination methods. The puzzling issue of the nature of massive neutrinos is addressed as well with explicit reference to the phenomenon of double beta-decay as a viable experimental tool to discriminate between Dirac’s and Majorana’s nature
A Proposal for Introducing Quantum Physics in the Footsteps of Einstein
No full textWe formulate a didactic proposal for introducing some fundamental concepts of quantum physics to advanced high school students, and to their teachers. The inspiration comes from some of the fundamental papers about the subject by Albert Einstein, in which many of these concepts, for example light quanta, wave-particle duality, and probability, were introduced for the first time, in a characteristically illuminating way. The proposal can be supplemented by a discussion of elementary tools of statistical physics, which are needed at some point. Preliminary results, both with students and teachers, are very promising
La genealogia accademica di Enrico Fermi
No full textThe history and main scientific features of the three main schools of physics operating in Italian Universities in the (Pisa, Rome and Turin) in the XIX century are briefly sketched, showing the role played by the local masters (Felici, Blaserna and Naccari) and by their most important students (Roiti, Bartoli and Stracciati, Macaluso and Corbino, Battelli and Puccianti). The different contributions given by all these teachers to the scientific formation of Enrico Fermi are discusse
Nonequilibrium properties of an atomic quantum dot coupled to a Bose-Einstein condensate
No full textWe study nonequilibrium properties of an atomic quantum
dot (AQD) coupled to a Bose-Einstein condensate (BEC) within Keldysh-
Green’s function formalism when the AQD level is varied harmonically
in time. Nonequilibrium features in the AQD energy absorption spec-
trum are the side peaks that develop as an effect of photon absorption
and emission. We show that atoms can be efficiently transferred from
the BEC into the AQD for the parameter regime of current experiments
with cold atoms
- …
