5,844 research outputs found
The curious case of large-N expansions on a (pseudo)sphere
We elucidate the large-N dynamics of one-dimensional sigma models with
spherical and hyperbolic target spaces and find a duality between the Lagrange
multiplier and the angular momentum. In the hyperbolic model we propose a new
class of operators based on the irreducible representations of hyperbolic
space. We also uncover unexpected zero modes which lead to the double scaling
of the 1/N expansion and explore these modes using Gelfand-Dikiy equations.Comment: 18 pages, 3 figure
Effective Non-Hermitian Hamiltonians for Studying Resonance Statistics in Open Disordered Systems
We briefly discuss construction of energy-dependent effective non-hermitian
hamiltonians for studying resonances in open disordered systemsComment: Latex, 20 pages, 1 fig. Expanded version of a talk at the Workshop on
Pseudo-Hermitian Hamiltonians in Quantum Physics IX, June 21-24 2010,
Zhejiang University, Hangzhou, China. Accepted for publication in the
Internationa Journal of Theoretical Physics (Springer Verlag
Effects of Bose-Einstein Condensation on forces among bodies sitting in a boson heat bath
We explore the consequences of Bose-Einstein condensation on
two-scalar-exchange mediated forces among bodies that sit in a boson gas. We
find that below the condensation temperature the range of the forces becomes
infinite while it is finite at temperatures above condensation.Comment: 10 pages, 2 figure
Spin-orbital Kondo decoherence by environmental effects in capacitively coupled quantum dot devices
Strong correlation effects in a capacitively coupled double quantum-dot setup
were previously shown to provide the possibility of both entangling spin-charge
degrees of freedom and realizing efficient spin-filtering operations by static
gate-voltage manipulations. Motivated by the use of such a device for quantum
computing, we study the influence of electromagnetic noise on a general
spin-orbital Kondo model, and investigate the conditions for observing
coherent, unitary transport, crucial to warrant efficient spin manipulations.
We find a rich phase diagram, where low-energy properties sensitively depend on
the impedance of the external environment and geometric parameters of the
system. Relevant energy scales related to the Kondo temperature are also
computed in a renormalization-group treatment, allowing to assess the
robustness of the device against environmental effects.Comment: 13 pages, 13 figures. Minor modifications in V
Assessment of seasonality in exposure to dioxins, furans and dioxin-like PCBs by using long-term food-consumption data
Addendum to Finite-size effects on multibody neutrino exchange
The interaction energy of the neutrons due to massless neutrino exchange in a
neutron star has recently been proved, using an effective theory, to be
extremely small and infrared-safe. Our comment here is of conceptual order: two
approaches to compute the total interaction energy density have recently been
proposed. Here, we study the connection between these two approaches. From CP
invariance, we argue that the resulting interaction energy has to be even in
the parameter , which expresses the static neutrino
potential created by a neutron medium of density .Comment: Latex file (Revtex), 9 pages, 1 figure, one reference change
Elastic precession of electronic spin states in interacting integer quantum Hall edge channels
We consider the effect of Coulomb interactions in the propagation of
electrons, prepared in arbitrary spin states, on chiral edge channels in the
integer quantum Hall regime. Electrons are injected and detected at the same
energy at different locations of the Hall bar, which is modeled as a chiral
Tomonaga-Luttinger liquid. The current is computed perturbatively in the
tunneling amplitudes, within a non-crossing approximation using exact solutions
of the interacting Green's functions. In the case of different channel
velocities, the spin precession effect is evaluated, and the role of
interaction parameters and wavevectors is discussed.Comment: 5 pages, 3 figure
PT-symmetry in honeycomb photonic lattices
We apply gain/loss to honeycomb photonic lattices and show that the
dispersion relation is identical to tachyons - particles with imaginary mass
that travel faster than the speed of light. This is accompanied by PT-symmetry
breaking in this structure. We further show that the PT-symmetry can be
restored by deforming the lattice
Long range neutrino forces in the cosmic relic neutrino background
Neutrinos mediate long range forces among macroscopic bodies in vacuum. When
the bodies are placed in the neutrino cosmic background, these forces are
modified. Indeed, at distances long compared to the scale , the relic
neutrinos completely screen off the 2-neutrino exchange force, whereas for
small distances the interaction remains unaffected.Comment: 8 pages, 2 figure
Dynamical Casimir-Polder interaction between an atom and surface plasmons
We investigate the time-dependent Casimir-Polder potential of a polarizable
two-level atom placed near a surface of arbitrary material, after a sudden
change in the parameters of the system. Different initial conditions are taken
into account. For an initially bare ground-state atom, the time-dependent
Casimir-Polder energy reveals how the atom is "being dressed" by virtual,
matter-assisted photons. We also study the transient behavior of the
Casimir-Polder interaction between the atom and the surface starting from a
partially dressed state, after an externally induced change in the atomic level
structure or transition dipoles. The Heisenberg equations are solved through an
iterative technique for both atomic and field operators in the medium-assisted
electromagnetic field quantization scheme. We analyze in particular how the
time evolution of the interaction energy depends on the optical properties of
the surface, in particular on the dispersion relationof surface plasmon
polaritons. The physical significance and the limits of validity of the
obtained results are discussed in detail.Comment: 12 pages, 8 figure
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