Combining gravity with the forces of the standard model on a cosmological scale

We prove the existence of a spectral resolution of the Wheeler-DeWitt equation when the underlying spacetime is a Friedman universe with flat spatial slices and where the matter fields are comprised of the strong interaction, with \SU(3) replaced by a general \SU(n), $n\ge 2$, and the electro-weak interaction. The wave functions are maps from $\R[4n+10]$ to a subspace of the antisymmetric Fock space, and one noteworthy result is that, whenever the electro-weak interaction is involved, the image of an eigenfunction is in general not one dimensional, i.e., in general it makes no sense specifying a fermion and looking for an eigenfunction the range of which is contained in the one dimensional vector space spanned by the fermion.Comment: 53 pages, v6: some typos correcte

Excitation and emission spectra of rubidium in rare-gas thin-films

To understand the optical properties of atoms in solid state matrices, the absorption, excitation and emission spectra of rubidium doped thin-films of argon, krypton and xenon were investigated in detail. A two-dimensional spectral analysis extends earlier reports on the excitation and emission properties of rubidium in rare-gas hosts. We found that the doped crystals of krypton and xenon exhibit a simple absorption-emission relation, whereas rubidium in argon showed more complicated spectral structures. Our sample preparation employed in the present work yielded different results for the Ar crystal, but our peak positions were consistent with the prediction based on the linear extrapolation of Xe and Kr data. We also observed a bleaching behavior in rubidium excitation spectra, which suggests a population transfer from one to another spectral feature due to hole-burning. The observed optical response implies that rubidium in rare-gas thin-films is detectable with extremely high sensitivity, possibly down to a single atom level, in low concentration samples.Comment: 7 pages, 5 figure

A gene influencing the composition of the culm in maize

1. A gene influencing the strength of culm in maize has been isolated and found to behave as a simple Mendelian recessive. The character has been called lazy and the factor pail\u27 involved has been degignated La la. 2. Lazy plants are distinguished from their normal sibs by their prostrate habit of growth. Their culms have a much lower breaking strength. 3. The culms of the lazy and normal plants have similar morphological structure, but differ histologically in the thickness of their cell walls. 4. The gene, lazy, exerts a marked influence on the composition of the culm. It greatly restricts the deposition of such structural materials as cellulose, lignin and pentosans. Lazy culms contain more moisture per unit weight of green tissue. During early development they also contain smaller amounts of nitrogen, water soluble material and total ash constituents on a green-weight basis. 5. Both the primary and secondary layers of the cell walls in corn become heavily lignified. All parts of the cell walls from the culms of normal plants contain much more lignin than do those of lazy plants. These differences are more apparent in the younger tissues. 6. The sequence of lignin formation is similar in normal and lazy culms. In parenchymatous tissues of both kinds of plant lignification apparently originates in the primary wall and later extends thru the secondary walls. In sclerenchymatous tissues the reverse relationship exists. 7. The lignin in the middle lamella and in the secondary walls differ in its structural appearance, the former being fibrillar and the latter granular in appearance. 8. All parts of the cell walls from the culms of lazy plants appear to contain less cellulose than do those of normal plants. The middle lamella of the young tissues of both normal and lazy plants appeared to be of a cellulosic nature and not pectinaceous. 9. The expressed juice of the lazy stalks contains a smaller quantity of ash and total solids. Its osmotic pressure is somewhat lower than that of the normal sibs. The ionizable constituents in the tissue fluids of the lazy culms, as shown by electrodialysis, also are lower. 10. The data indicate that the prostrate habit of growth, characteristic of the lazy plants, is due to a physical ralationship between the strength of the supporting tissue and the weight of the plant to be supported. This relationship evidently results from a restricted deposition of the structural materials of the dry matter per unit weight of green material

Ultrafast circular polarization oscillations in spin-polarized vertical-cavity surface-emitting laser devices

Spin-polarized lasers offer new encouraging possibilities for future devices. We investigate the polarization dynamics of electrically pumped vertical-cavity surface-emitting lasers after additional spin injection at room temperature. We find that the circular polarization degree exhibits faster dynamics than the emitted light. Moreover the experimental results demonstrate a strongly damped ultrafast circular polarization oscillation due to spin injection with an oscillation frequency of approximately 11GHz depending on the birefringence in the VCSEL device. We compare our experimental results with theoretical calculations based on rate-equations. This allows us to predict undamped long persisting ultrafast polarization oscillations, which reveal the potential of spin-VCSELs for ultrafast modulation applications

Birefringence controlled room-temperature picosecond spin dynamics close to the threshold of vertical-cavity surface-emitting laser devices

We analyze the spin-induced circular polarization dynamics at the threshold of vertical-cavity surface-emitting lasers at room-temperature using a hybrid excitation combining electrically pumping without spin preference and spin-polarized optical injection. After a short pulse of spin-polarized excitation, fast oscillations of the circular polarization degree (CPD) are observed within the relaxation oscillations. A theoretical investigation of this behavior on the basis of a rate equation model shows that these fast oscillations of CPD could be suppressed by means of a reduction of the birefringence of the laser cavity