Characterization of the Vacuum Birefringence Polarimeter at BMV: Dynamical Cavity Mirror Birefringence

We present the current status and outlook of the optical characterization of the polarimeter at the Bir\'{e}fringence Magn\'etique du Vide (BMV) experiment. BMV is a polarimetric search for the QED predicted anisotropy of vacuum in the presence of external electromagnetic fields. The main challenge faced in this fundamental test is the measurement of polarization ellipticity on the order of ${10^{-15}}$ induced in linearly polarized laser field per pass through a magnetic field having an amplitude and length ${B^{2}L=100\,\mathrm{T}^{2}\mathrm{m}}$. This challenge is addressed by understanding the noise sources in precision cavity-enhanced polarimetry. In this paper we discuss the first investigation of dynamical birefringence in the signal-enhancing cavity as a result of cavity mirror motion.Comment: To appear in the 2019 CPEM special issue of IEEE Transactions on Instrumentation and Measuremen

Noise characterization for resonantly-enhanced polarimetric vacuum magnetic-birefringence experiments

In this work we present data characterizing the sensitivity of the Bir\'{e}fringence Magnetique du Vide (BMV) instrument. BMV is an experiment attempting to measure vacuum magnetic birefringence (VMB) via the measurement of an ellipticity induced in a linearly polarized laser field propagating through a birefringent region of vacuum in the presence of an external magnetic field. Correlated measurements of laser noise alongside the measurement in the main detection channel allow us to separate measured sensing noise from the inherent birefringence noise of the apparatus. To this end we model different sources of sensing noise for cavity-enhanced polarimetry experiments, such as BMV. Our goal is to determine the main sources of noise, clarifying the limiting factors of such an apparatus. We find our noise models are compatible with the measured sensitivity of BMV. In this context we compare the phase sensitivity of separate-arm interferometers to that of a polarimetry apparatus for the discussion of current and future VMB measurements

An investigation for the development of an integrated optical data preprocessor

A laboratory model of a 16 channel integrated optical data preprocessor was fabricated and tested in response to a need for a device to evaluate the outputs of a set of remote sensors. It does this by accepting the outputs of these sensors, in parallel, as the components of a multidimensional vector descriptive of the data and comparing this vector to one or more reference vectors which are used to classify the data set. The comparison is performed by taking the difference between the signal and reference vectors. The preprocessor is wholly integrated upon the surface of a LiNbO3 single crystal with the exceptions of the source and the detector. He-Ne laser light is coupled in and out of the waveguide by prism couplers. The integrated optical circuit consists of a titanium infused waveguide pattern, electrode structures and grating beam splitters. The waveguide and electrode patterns, by virtue of their complexity, make the vector subtraction device the most complex integrated optical structure fabricated to date

Gamma ray observations of the galactic center and some possible point sources

Observations of galactic center radiation and possible point sources obtained by gamma ray telescope flown on three balloon flight

Extending Romanovski polynomials in quantum mechanics

Some extensions of the (third-class) Romanovski polynomials (also called Romanovski/pseudo-Jacobi polynomials), which appear in bound-state wavefunctions of rationally-extended Scarf II and Rosen-Morse I potentials, are considered. For the former potentials, the generalized polynomials satisfy a finite orthogonality relation, while for the latter an infinite set of relations among polynomials with degree-dependent parameters is obtained. Both types of relations are counterparts of those known for conventional polynomials. In the absence of any direct information on the zeros of the Romanovski polynomials present in denominators, the regularity of the constructed potentials is checked by taking advantage of the disconjugacy properties of second-order differential equations of Schr\"odinger type. It is also shown that on going from Scarf I to Scarf II or from Rosen-Morse II to Rosen-Morse I potentials, the variety of rational extensions is narrowed down from types I, II, and III to type III only.Comment: 25 pages, no figure, small changes, 3 additional references, published versio

Genetic and physical mapping of DNA replication origins in Haloferax volcanii

The halophilic archaeon Haloferax volcanii has a multireplicon genome, consisting of a main chromosome, three secondary chromosomes, and a plasmid. Genes for the initiator protein Cdc6/Orc1, which are commonly located adjacent to archaeal origins of DNA replication, are found on all replicons except plasmid pHV2. However, prediction of DNA replication origins in H. volcanii is complicated by the fact that this species has no less than 14 cdc6/orc1 genes. We have used a combination of genetic, biochemical, and bioinformatic approaches to map DNA replication origins in H. volcanii. Five autonomously replicating sequences were found adjacent to cdc6/orc1 genes and replication initiation point mapping was used to confirm that these sequences function as bidirectional DNA replication origins in vivo. Pulsed field gel analyses revealed that cdc6/orc1-associated replication origins are distributed not only on the main chromosome (2.9 Mb) but also on pHV1 (86 kb), pHV3 (442 kb), and pHV4 (690 kb) replicons. Gene inactivation studies indicate that linkage of the initiator gene to the origin is not required for replication initiation, and genetic tests with autonomously replicating plasmids suggest that the origin located on pHV1 and pHV4 may be dominant to the principal chromosomal origin. The replication origins we have identified appear to show a functional hierarchy or differential usage, which might reflect the different replication requirements of their respective chromosomes. We propose that duplication of H. volcanii replication origins was a prerequisite for the multireplicon structure of this genome, and that this might provide a means for chromosome-specific replication control under certain growth conditions. Our observations also suggest that H. volcanii is an ideal organism for studying how replication of four replicons is regulated in the context of the archaeal cell cycle. © 2007 Norais et al

Multiple synchrotron self-Compton modeling of gamma-ray flares in 3C 279

The correlation often observed in blazars between optical-to-radio outbursts and gamma-ray flares suggests that the high-energy emission region shall be co-spatial with the radio knots, several parsecs away from the central engine. This would prevent the important contribution at high-energies from the Compton scattering of seed photons from the accretion disk and the broad-line region that is generally used to model the spectral energy distribution of low-frequency peaking blazars. While a pure synchrotron self-Compton model has so far failed to explain the observed gamma-ray emission of a flat spectrum radio quasar like 3C 279, the inclusion of the effect of multiple inverse-Compton scattering might solve the apparent paradox. Here, we present for the first time a physical, self-consistent SSC modeling of a series of shock-waves in the jet of 3C 279. We show that the analytic description of the high-energy emission from multiple inverse-Compton scatterings in the Klein-Nishina limit can fairly well account for the observed gamma-ray spectrum of 3C 279 in flaring states.Comment: 6 pages, 3 figures, proceedings of "Beamed and Unbeamed Gamma-rays from Galaxies", 11-15 April 2011, Finland. To be published in the Journal of Physics: Conference Serie

Variables in Globular Cluster NGC 5024

We present the results of a commissioning campaign to observe Galactic globular clusters for the search of microlensing events. The central 10' X 10' region of the globular cluster NGC 5024 was monitored using the 2-m Himalayan Chandra Telescope in R-band for a period of about 8 hours on 24 March 2010. Light curves were obtained for nearly 10,000 stars, using a modified Difference Image Analysis (DIA) technique. We identified all known variables within our field of view and revised periods and status of some previously reported short-period variables. We report about eighty new variable sources and present their equatorial coordinates, periods, light curves and possible types. Out of these, 16 are SX Phe stars, 10 are W UMa-type stars, 14 are probable RR Lyrae stars and 2 are detached eclipsing binaries. Nine of the newly discovered SX Phe stars and two eclipsing binaries belong to the Blue Straggler Star (BSS) population.Comment: 29 pages, 22 figures, replaced with rewritten data reduction par