Carrier-wave Rabi flopping signatures in high-order harmonic generation for alkali atoms

We present the first theoretical investigation of carrier-wave Rabi flopping in real atoms by employing numerical simulations of high-order harmonic generation (HHG) in alkali species. Given the short HHG cutoff, related to the low saturation intensity, we concentrate on the features of the third harmonic of sodium (Na) and potassium (K) atoms. For pulse areas of 2$\pi$ and Na atoms, a characteristic unique peak appears, which, after analyzing the ground state population, we correlate with the conventional Rabi flopping. On the other hand, for larger pulse areas, carrier-wave Rabi flopping occurs, and is associated with a more complex structure in the third harmonic. These new characteristics observed in K atoms indicate the breakdown of the area theorem, as was already demonstrated under similar circumstances in narrow band gap semiconductors

Quantum, Multi-Body Effects and Nuclear Reaction Rates in Plasmas

Detailed calculations of the contribution from off-shell effects to the quasiclassical tunneling of fusing particles are provided. It is shown that these effects change the Gamow rates of certain nuclear reactions in dense plasma by several orders of magnitude.Comment: 11 pages; change of content: added clarification of one of the important steps in the derivatio

Unstable states in QED of strong magnetic fields

We question the use of stable asymptotic scattering states in QED of strong magnetic fields. To correctly describe excited Landau states and photons above the pair creation threshold the asymptotic fields are chosen as generalized Licht fields. In this way the off-shell behavior of unstable particles is automatically taken into account, and the resonant divergences that occur in scattering cross sections in the presence of a strong external magnetic field are avoided. While in a limiting case the conventional electron propagator with Breit-Wigner form is obtained, in this formalism it is also possible to calculate $S$-matrix elements with external unstable particles.Comment: Revtex, 7 pages. To appear in Phys. Rev. D53(2

Heat Bath Particle Number Spectrum

We calculate the number spectrum of particles radiated during a scattering into a heat bath using the thermal largest-time equation and the Dyson-Schwinger equation. We show how one can systematically calculate {d}/{d\omega} to any order using modified real time finite-temperature diagrams. Our approach is demonstrated on a simple model where two scalar particles scatter, within a photon-electron heat bath, into a pair of charged particles and it is shown how to calculate the resulting changes in the number spectra of the photons and electrons.Comment: 29 pages, LaTeX; 14 figure

KMS conditions for 4-point Green functions at finite temperature

We study the 4-point function in the Keldysh formalism of the closed time path formulation of real time finite temperature field theory. We derive the KMS conditions for these functions and discuss the number of 4-point functions that are independent. We define a set of `physical' functions which are linear combinations of the usual Keldysh functions. We show that these functions satisfy simple KMS conditions. In addition, we consider a set of integral equations which represent a resummation of ladder graphs. We show that these integral equations decouple when one uses the physical functions that we have defined. We discuss the generalization of these results to QED.Comment: 17 pages in Revtex with 2 figure

Hamiltonian reductions of free particles under polar actions of compact Lie groups

Classical and quantum Hamiltonian reductions of free geodesic systems of complete Riemannian manifolds are investigated. The reduced systems are described under the assumption that the underlying compact symmetry group acts in a polar manner in the sense that there exist regularly embedded, closed, connected submanifolds meeting all orbits orthogonally in the configuration space. Hyperpolar actions on Lie groups and on symmetric spaces lead to families of integrable systems of spin Calogero-Sutherland type.Comment: 15 pages, minor correction and updated references in v

Quantum mechanics is about quantum information

I argue that quantum mechanics is fundamentally a theory about the representation and manipulation of information, not a theory about the mechanics of nonclassical waves or particles. The notion of quantum information is to be understood as a new physical primitive -- just as, following Einstein's special theory of relativity, a field is no longer regarded as the physical manifestation of vibrations in a mechanical medium, but recognized as a new physical primitive in its own right.Comment: 17 pages, forthcoming in Foundations of Physics Festschrift issue for James Cushing. Revised version: some paragraphs have been added to the final section clarifying the argument, and various minor clarifying remarks have been added throughout the tex

A Combined Spitzer and Chandra Survey of Young Stellar Objects in the Serpens Cloud Core

We present Spitzer and Chandra observations of the nearby (~260 pc) embedded stellar cluster in the Serpens Cloud Core. We observed, using Spitzer's IRAC and MIPS instruments, in six wavelength bands from 3 to 70 ${\mu}m$, to detect thermal emission from circumstellar disks and protostellar envelopes, and to classify stars using color-color diagrams and spectral energy distributions (SEDs). These data are combined with Chandra observations to examine the effects of circumstellar disks on stellar X-ray properties. Young diskless stars were also identified from their increased X-ray emission. We have identified 138 YSOs in Serpens: 22 class 0/I, 16 flat spectrum, 62 class II, 17 transition disk, and 21 class III stars; 60 of which exhibit X-ray emission. Our primary results are the following: 1.) ten protostars detected previously in the sub-millimeter are detected at lambda < 24 microns, seven at lambda < 8 microns, 2.) the protostars are more closely grouped than more evolved YSOs (median separation : ~0.024 pc, and 3.) the luminosity and temperature of the X-ray emitting plasma around these YSOs does not show any significant dependence on evolutionary class. We combine the infrared derived values of AK and X-ray values of NH for 8 class III objects and find that the column density of hydrogen gas per mag of extinctions is less than half the standard interstellar value, for AK > 1. This may be the result of grain growth through coagulation and/or the accretion of volatiles in the Serpens cloud core.Comment: 69 pages, 16 figures, accepted to ApJ. Higher Resolution Figures at: http://www.cfa.harvard.edu/~ewinston