Measurement of Parity Violation in the Early Universe using Gravitational-wave Detectors

A stochastic gravitational-wave background (SGWB) is expected to arise from the superposition of many independent and unresolved gravitational-wave signals, of either cosmological or astrophysical origin. Some cosmological models (characterized, for instance, by a pseudo-scalar inflaton, or by some modification of gravity) break parity, leading to a polarized SGWB. We present a new technique to measure this parity violation, which we then apply to the recent results from LIGO to produce the first upper limit on parity violation in the SGWB, assuming a generic power-law SGWB spectrum across the LIGO sensitive frequency region. We also estimate sensitivity to parity violation of the future generations of gravitational-wave detectors, both for a power-law spectrum and for a model of axion inflation. This technique offers a new way of differentiating between the cosmological and astrophysical sources of the isotropic SGWB, as astrophysical sources are not expected to produce a polarized SGWB.Comment: 5 pages, 2 figures, 1 tabl

Observable non-gaussianity from gauge field production in slow roll inflation, and a challenging connection with magnetogenesis

In any realistic particle physics model of inflation, the inflaton can be expected to couple to other fields. We consider a model with a dilaton-like coupling between a U(1) gauge field and a scalar inflaton. We show that this coupling can result in observable non-gaussianity, even in the conventional regime where inflation is supported by a single scalar slowly rolling on a smooth potential: the time dependent inflaton condensate leads to amplification of the large-scale gauge field fluctuations, which can feed-back into the scalar/tensor cosmological perturbations. In the squeezed limit, the resulting bispectrum is close to the local one, but it shows a sizable and characteristic quadrupolar dependence on the angle between the shorter and the larger modes in the correlation. Observable non-gaussianity is obtained in a regime where perturbation theory is under control. If the gauge field is identified with the electromagnetic field, the model that we study is a realization of the magnetogenesis idea originally proposed by Ratra, and widely studied. This identification (which is not necessary for the non-gaussianity production) is however problematic in light of a strong coupling problem already noted in the literature.Comment: 28 pages, no figures. Final versio

Parametric attosecond pulse amplification far from the ionization threshold from high order harmonic generation in He+^+

Parametric amplification of attosecond coherent pulses around 100 eV at the single-atom level is demonstrated for the first time by using the 3D time-dependent Schr{\"o}dinger equation in high-harmonic generation processes from excited states of He$^+$. We present the attosecond dynamics of the amplification process far from the ionization threshold and resolve the physics behind it. The amplification of a particular central photon energy requires the seed XUV pulses to be perfectly synchronized in time with the driving laser field for stimulated recombination to the He$^+$ ground state and is only produced in a few specific laser cycles in agreement with the experimental measurements. Our simulations show that the amplified photon energy region can be controlled by varying the peak intensity of the laser field. Our results pave the way to the realization of compact attosecond pulse intense XUV lasers with broad applications

Carcinogenesis in tissue culture. 22. Malignant transformation of cloned rat liver cells treated in culture with 4-dimethylaminoazobenzene and properties of the transformed cells

Cultured rat liver cells which were cloned from a single cell were transformed into malignant cells by a chemical carcinogen, 4-dimethylaminoazobenzene (DAB). The DAB-transformed cells produced tumors when back-transplanted into new-born rats but the carcinogen-untreated control cells did not. Characteristics of the transformed liver cells were compared to those of DAB-untreated control cells in regard to the morphology, the consumption of DAB from the culture medium by the cells, the incorporation of 3H.DAB into the cells, and the aggregate.forming ability of the cells in rotation culture. The results showed that no significant parameter of malig. nant transformation in culture was detectable except the tumorigenicity of the transformed cells upon the inoculation into animals.</p

An x-ray detector using PIN photodiodes for the axion helioscope

An x-ray detector for a solar axion search was developed. The detector is operated at 60K in a cryostat of a superconducting magnet. Special care was paid to microphonic noise immunity and mechanical structure against thermal contraction. The detector consists of an array of PIN photodiodes and tailor made preamplifiers. The size of each PIN photodiode is $11\times 11\times 0.5\ {\rm mm^3}$ and 16 pieces are used for the detector. The detector consists of two parts, the front-end part being operated at a temperature of 60K and the main part in room temperature. Under these circumstances, the detector achieved 1.0 keV resolution in FWHM, 2.5 keV threshold and 6\times 10^{-5} counts sec^{-1} keV^{-1} cm^{-2} background level.Comment: 8 pages, 5 figures, submitted to Nucl. Instr. Meth.

Diagnostic arthroscopy in the treatment of minimally displaced lateral humeral condyle fractures in children

AbstractIntroductionIn minimally displaced pediatric lateral humeral condyle fractures, plain radiography cannot be used for accurate differential diagnosis of the cartilage lesion, and other imaging methods have demerits in their accuracy and their accessibility. The purpose of this study was to investigate the usefulness of arthroscopy to diagnose cartilage displacement in minimally displaced fractures.Materials and methodsNine children with minimally displaced lateral humeral condyle fractures, an average of 6.6 years old, underwent combined arthroscopy and fixation surgery. Percutaneous fixation was performed with nondisplaced articular surface according to the arthroscopic findings, while in case of displaced fracture under arthroscopy, open fixation was preferred. The difference between the arthroscopic and radiographic findings was investigated.ResultsArticular surface could be arthroscopically visualized in all patients. Under arthroscopy, cartilage hinges were maintained in seven cases and disrupted in two. Nondisplaced cartilage disruption was noted in one of these two cases, and percutaneous fixation was performed. A displaced articular surface was noted in the other one, where the patient underwent open surgery. At the last follow-up, an average of 14.7 months postoperatively, union and wide range of motion had been achieved without any complications.ConclusionDiagnosis of fracture displacement by merely using plain radiography was considered to be insufficient for minimally displaced cases. Diagnostic arthroscopy aided in the appropriate selection of either a percutaneous or open fixation method.Level of evidenceLevel IV, therapeutic case series