14,125 research outputs found
Theory of Resonant Inelastic X-ray Scattering by Collective Magnetic Excitations
I present a tractable theory for the Resonant Inelastic X-ray Scattering
(RIXS) spectral function of magnons. The low-energy transition operator is
written as a product of local spin operators times fundamental x-ray absorption
spectra. This leads to simple selection rules for the magnetic cross section.
The scattering cross section linear (quadratic) in spin operators is
proportional to the magnetic circular (linear) dichroic absorption. RIXS is a
novel tool to measure magnetic quasi particles (magnons) and the incoherent
spectral weight, as well as multiple magnons up to very high energy losses, in
small samples, thin films and multilayers, complementary to Neutron scattering
Assumptions and Data Sources for the Construction of a Multi-Region Input-Output Table for Indonesia
Structure and magnetic properties of Nd2Co17-xGax compounds studied by magnetic measurements and neutron diffraction
A Physical Realization of the Generalized PT-, C-, and CPT-Symmetries and the Position Operator for Klein-Gordon Fields
Generalized parity (P), time-reversal (T), and charge-conjugation
(C)operators were initially definedin the study of the pseudo-Hermitian
Hamiltonians. We construct a concrete realization of these operators for
Klein-Gordon fields and show that in this realization PT and C operators
respectively correspond to the ordinary time-reversal and charge-grading
operations. Furthermore, we present a complete description of the quantum
mechanics of Klein-Gordon fields that is based on the construction of a Hilbert
space with a relativistically invariant, positive-definite, and conserved inner
product. In particular we offer a natural construction of a position operator
and the corresponding localized and coherent states. The restriction of this
position operator to the positive-frequency fields coincides with the
Newton-Wigner operator. Our approach does not rely on the conventional
restriction to positive-frequency fields. Yet it provides a consistent quantum
mechanical description of Klein-Gordon fields with a genuine probabilistic
interpretation.Comment: 20 pages, published versio
Dissipative effects from transport and viscous hydrodynamics
We compare 2->2 covariant transport theory and causal Israel-Stewart
hydrodynamics in 2+1D longitudinally boost invariant geometry with RHIC-like
initial conditions and a conformal e = 3p equation of state. The pressure
evolution in the center of the collision zone and the final differential
elliptic flow v2(pT) from the two theories agree remarkably well for a small
shear viscosity to entropy density ratio eta/s ~ 1/(4 pi), and also for a large
cross section sigma ~ 50 mb. A key to this agreement is keeping ALL terms in
the Israel-Stewart equations of motion. Our results indicate promising
prospects for the applicability of Israel-Stewart dissipative hydrodynamics at
RHIC, provided the shear viscosity of hot and dense quark-gluon matter is
indeed very small for the relevant temperatures T ~ 200-500 MeV.Comment: Presentation at Quark Matter 2008. 4 pages, 3 figure
- …