Geometry, Frustration, and Exotic Order in Magnetic Systems
... interaction gives rise to frustration. As will be discussed, experimental signatures of the
frustration include the retention of entropy at very low temperatures (when naively we
expect it should tend to zero); the failure to develop long range magnetic order despite a
ferromagnetic Curie constant; ...
The physics of dipolar bosonic quantum gases
... where D is the dimensionality of the system and r0 some shortdistance cutoff, converges at large distances. For interactions
decaying at large distances as 1/r n , this implies that one
needs to have D < n in order to consider the interaction
to be short range. Therefore, the dipole–dipole interacti ...
Topological phases and polaron physics in ultra cold quantum gases
... typically means that we can write down a Hamiltonian Ĥ (or a Lagrangian) which describes
the relevant microscopic degrees of freedom. However, this by far does not mean that all
the physics is well understood at moderate energies! The interplay of many indistinguishable
particles – of the order of ...
Number Fluctuations and Phase Diffusion in a Bose
... sical textbook on statistical mechanics by K. Huang : “Bose-Einstein condensation can only occur
when the particle number is conserved. For example, photons cannot condense. They have a simpler
alternative, namely, to simply disappear in the vacuum.”. The reasoning behind this statement is that
The Thomas-Fermi model: momentum expectation values
... involve the contributions of strongly bound electrons,
the inhomogeneity of the electron density and oscillations. The first of them may be very substantial and
will be considered in section 4. The correction for the
electron density inhomogeneity has the same relative
order as the exchange contribu ...
Casimir and Critical Casimir effects An overview Sergio Ciliberto
... (a) the bulk, e.g. symmetries of the interaction, kind of order parameter
(b) the surfaces of the wall, e.g. the symmetries of the bulk which they break
(c) The shape of the walls
(a) and (b) define the bulk and surface universality classes of the confined system
lundi 2 novembre 2015
Lectures on Conformal Field Theory arXiv:1511.04074v2 [hep
... of conformal field theories has advanced significantly. Consequently, conformal field
theory is a very broad subject. This is not the first set of lecture notes on this topic,
nor will it be the last. So why have I bothered making these notes available when there
are already so many choices?
There a ...
- Sussex Research Online
... theory for a simple two mode interferometer showing that such an interferometer can be used to
measure the mean values and covariance matrix for the spin operators involved in entanglement
tests for the two mode bosonic system. The treatment is also generalized to cover multi-mode
interferometry. Th ...
Nematic Fermi Fluids in Condensed Matter Physics
... Strongly correlated electron systems are mostly defined by what they are not: they are not
gases of weakly interacting quasiparticles (QPs) (Fermi gases), but they are still electron
fluids (i.e., not insulators). Perhaps classical liquids are a good analogy. They are so
different locally from a gas ...
Theory of ultracold atomic Fermi gases
... 共Published 2 October 2008兲
The physics of quantum degenerate atomic Fermi gases in uniform as well as in harmonically trapped
configurations is reviewed from a theoretical perspective. Emphasis is given to the effect of
interactions that play a crucial role, bringing the gas into a superfluid phase ...
... mechanisms were dramatically suppressed by the interplay of the Pauli exclusion principle
and the large size of the Feshbach molecules. So what we have got is a Hilbert space which
consists of atomic levels plus one single molecular level resonantly coupled to two colliding
atoms. All other molecula ...
Photon echoes for a system of large negative spin and few mean
... field with small mean photon number in a closed cavity. This particular example in a crowded active field
of research has been overlooked. The interaction of TLMs interacting with a field in a closed cavity is well
known and has been covered extensively, as will be seen in the next section. An exami ...
The Ising model (/ˈaɪsɪŋ/; German: [ˈiːzɪŋ]), named after the physicist Ernst Ising, is a mathematical model of ferromagnetism in statistical mechanics. The model consists of discrete variables that represent magnetic dipole moments of atomic spins that can be in one of two states (+1 or −1). The spins are arranged in a graph, usually a lattice, allowing each spin to interact with its neighbors. The model allows the identification of phase transitions, as a simplified model of reality. The two-dimensional square-lattice Ising model is one of the simplest statistical models to show a phase transition.The Ising model was invented by the physicist Wilhelm Lenz (1920), who gave it as a problem to his student Ernst Ising. The one-dimensional Ising model has no phase transition and was solved by Ising (1925) himself in his 1924 thesis. The two-dimensional square lattice Ising model is much harder, and was given an analytic description much later, by Lars Onsager (1944). It is usually solved by a transfer-matrix method, although there exist different approaches, more related to quantum field theory.In dimensions greater than four, the phase transition of the Ising model is described by mean field theory.