53,283 research outputs found
Heisenberg and Modular Invariance of N=2 Conformal Field Theory
We present a theta function representation of the twisted characters for the
rational N=2 superconformal field theory, and discuss the Jacobi-form like
functional properties of these characters for a fixed central charge under the
action of a finite Heisenberg group and modular transformations.Comment: 21 pages, Latex, 1 figure; minor typos corrected--Journal versio
Topological Superfluid Transition Induced by Periodically Driven Optical Lattice
We propose a scenario to create topological superfluid in a periodically
driven two-dimensional square optical lattice. We study the phase diagram of a
spin-orbit coupled s-wave pairing superfluid in a periodically driven
two-dimensional square optical lattice. We find that a phase transition from a
trivial superfluid to a topological superfluid occurs when the potentials of
the optical lattices are periodically changed. The topological phase is called
Floquet topological superfluid and can host Majorana fermions.Comment: 6 pages, 1 figure
Entanglement fidelity and measurement of entanglement preserving in quantum processes
The entanglement fidelity provides a measure of how well the entanglement
between two subsystems is preserved in a quantum process. By using a simple
model we show that in some cases this quantity in its original definition fails
in the measurement of the entanglement preserving. On the contrary, the
modified entanglement fidelity, obtained by using a proper local unitary
transformation on a subsystem, is shown to exhibit the behavior similar to that
of the concurrence in the quantum evolution.Comment: 4 pages, 2 figures. v2: repaired a severe oversight, removed an
incorrect claim, added references; v3: version accepted for publication in
Phys. Rev.
Simulating and Detecting the Quantum Spin Hall Effect in Kagom\'{e} Optical Lattice
We propose a model which includes a nearest-neighbor intrinsic spin-orbit
coupling and a dimer Hamiltonian in the Kagom\'{e} lattice and promises to host
the transition from the quantum spin Hall insulator to the normal insulator. In
addition, we design an experimental scheme to simulate and detect this
transition in the ultracold atom system. The lattice intrinsic spin-orbit
coupling is generated via the laser-induced-gauge-field method. Furthermore, we
establish the connection between the spin Chern number and the spin-atomic
density which enables us to detect the topological quantum spin Hall insulator
directly by the standard density-profile technique used in the atomic systems.Comment: 8 pages, 6 figure
The non-centrosymmetric lamellar phase in blends of ABC triblock and ac diblock copolymers
The phase behaviour of blends of ABC triblock and ac diblock copolymers is
examined using self-consistent field theory. Several equilibrium lamellar
structures are observed, depending on the volume fraction of the diblocks,
phi_2, the monomer interactions, and the degrees of polymerization of the
copolymers. For segregations just above the order-disorder transition the
triblocks and diblocks mix together to form centrosymmetric lamellae. As the
segregation is increased the triblocks and diblocks spatially separate either
by macrophase-separating, or by forming a non-centrosymmetric (NCS) phase of
alternating layers of triblock and diblock (...ABCcaABCca...). The NCS phase is
stable over a narrow region near phi_2=0.4. This region is widest near the
critical point on the phase coexistence curve and narrows to terminate at a
triple point at higher segregation. Above the triple point there is two-phase
coexistence between almost pure triblock and diblock phases. The theoretical
phase diagram is consistent with experiments.Comment: 9 pages, 8 figures, submitted to Macromolecule
Experimentally observed evolution between dynamic patterns and intrinsic localized modes in a driven nonlinear electrical cyclic lattice
Locked intrinsic localized modes (ILMs) and large amplitude lattice spatial
modes (LSMs) have been experimentally measured for a driven 1-D nonlinear
cyclic electric transmission line, where the nonlinear element is a saturable
capacitor. Depending on the number of cells and electrical lattice damping a
LSM of fixed shape can be tuned across the modal spectrum. Interestingly, by
tuning the driver frequency away from this spectrum an LSM can be continuously
converted into ILMs and visa versa. The differences in pattern formation
between simulations and experimental findings are due to a low concentration of
impurities. Through this novel nonlinear excitation and switching channel in
cyclic lattices either energy balanced or unbalanced LSMs and ILMs may occur.
Because of the general nature of these dynamical results for nonintegrable
lattices applications are to be expected. The ultimate stability of driven aero
machinery containing nonlinear periodic structures may be one example.Comment: 7 pages 7 figure
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