Broad Band Optical Polarimetric Study of IC 1805

We present the BVR broad band polarimetric observations of 51 stars belonging to the young open cluster IC 1805. Along with the photometric data from the literature we have modeled and subtracted the foreground dust contribution from the maximum polarization (P_{max}) and colour excess (E_{B-V}). The mean value of the P_max for intracluster medium and the foreground are found to be 5.008 +/-0.005 % and 4.865 +/-0.022 % respectively. Moreover, the mean value of the wavelength of maximum polarization (lambda_{max}) for intracluster medium is 0.541 +/- 0.003 micro m, which is quite similar as the general interstellar medium (ISM). The resulting intracluster dust component is found to have negligible polarization efficiency as compared to interstellar dust. Some of the observed stars in IC 1805 have shown the indication of intrinsic polarization in their measurements.Comment: 8 pages, 7 figures, Accepted for publication in MNRA

A Statistical and Multiwavelength Photometric Analysis of a Young Embedded Open Star Cluster: IC 1590

We present a statistical and multiwavelength photometric studies of young open cluster IC 1590. We identified 91 cluster members using $Gaia$ DR3 astrometry data using ensemble-based unsupervised machine learning techniques. From $Gaia$ EDR3 data, we estimate the best-fitted parameters for IC 1590 using the Automated Stellar Cluster Analysis package (ASteCA) yielding the distance $d$ $\sim$ 2.87 $\pm$ 0.02 Kpc, age $\sim$ 3.54 $\pm$ 0.05 Myr, metallicity $z$ $\sim$ 0.0212 $\pm$ 0.003, binarity value of $\sim$ 0.558, and extinction $A_v$ $\sim$ 1.252 $\pm$ 0.4 mag for an $R_v$ value of $\sim$ 3.322 $\pm$ 0.23. We estimate the initial mass function slope of the cluster to be $\alpha$ = 1.081 $\pm$ 0.112 for single stars and $\alpha$ = 1.490 $\pm$ 0.051 for a binary fraction of $\sim$ 0.558 in the mass range 1 M$_{\odot}$ $\leq$ m(M$_{\odot}$) $\leq$ 100 M$_{\odot}$. The $G$-band luminosity function slope is estimated to be $\sim$ 0.33 $\pm$ 0.09. We use $(J-H)$ versus $(H-K_s)$ color-color diagram to identify young stellar objects (YSOs). We found that all the identified YSOs have ages $\leq$ 2 Myr and masses $\sim$ 0.35 - 5.5 M$_{\odot}$. We also fit the radial surface density profile. Using the galpy we performed orbit analysis of the cluster. The extinction map for the cluster region has been generated using the PNICER technique and it is almost similar to the dust structure obtained from the 500 $\mu$$m$ dust continuum emissions map of $Herschel$ SPIRE. We finally at the end discussed the star formation scenario in the cluster region

Coexistence of magnetism and superconductivity in a t-J bilayer

We investigate coexistence of antiferromagnetic and superconducting correlations in bilayered materials using a two-dimensional t-J model with couplings across the layers using variational Monte Carlo calculations. It is found that the underdoped regime supports a coexisting phase, beyond which the (d-wave) superconducting state becomes stable. Further, the effects of interplanar coupling parameters on the magnetic and superconducting correlations as a function of hole doping are studied in details. The magnetic correlations are found to diminish with increasing interplanar hopping away from half filling, while the exchange across the layers strengthens interplanar antiferromagnetic correlations both at and away from half filling. The superconducting correlations show more interesting features where larger interplanar hopping considerably reduces planar correlations at optimal doping, while an opposite behaviour, i.e. stabilisation of the superconducting state is realised in the overdoped regime, with the interplanar exchange all the while playing a dormant role.Comment: 8 pages, 9 figures, RevTex4, Submitted to Phys. Rev.

Polarization in young open cluster NGC 6823

We present multiwavelength linear polarimetric observations of 104 stars towards the region of young open cluster NGC 6823. The polarization towards NGC 6823 is dominated by foreground dust grains and we found the evidence for the presence of several layers of dust towards the line of sight. The first layer of dust is located approximately within 200 pc towards the cluster, which is much closer to the Sun than the cluster (~ 2.1 kpc). The radial distribution of the position angles for the member stars are found to show a systematic change while the polarization found to reduce towards the outer parts of the cluster and the average position angle of coronal region of the cluster is very close to the inclination of the Galactic parallel (~ 32 degree). The size distribution of the grains within NGC 6823 is similar to those in general interstellar medium. The patchy distribution of foreground dust grains are suggested to be mainly responsible for the both differential reddening and polarization towards NGC 6823. The majority of the observed stars do not show the evidence of intrinsic polarization in their light.Comment: 16 pages, 6 tables, 11 figures, Accepted for publication in MNRA

Physical Electronics and Surface Physics

Contains reports on one research project.Joint Services Electronics Program (Contract DAAB07-71-C-0300

The Barrier Method: A Technique for Calculating Very Long Transition Times

In many dynamical systems there is a large separation of time scales between typical events and "rare" events which can be the cases of interest. Rare-event rates are quite difficult to compute numerically, but they are of considerable practical importance in many fields: for example transition times in chemical physics and extinction times in epidemiology can be very long, but are quite important. We present a very fast numerical technique that can be used to find long transition times (very small rates) in low-dimensional systems, even if they lack detailed balance. We illustrate the method for a bistable non-equilibrium system introduced by Maier and Stein and a two-dimensional (in parameter space) epidemiology model.Comment: 20 pages, 8 figure

Computation of nucleation of a non-equilibrium first-order phase transition using a rare-event algorithm

We introduce a new Forward-Flux Sampling in Time (FFST) algorithm to efficiently measure transition times in rare-event processes in non-equilibrium systems, and apply it to study the first-order (discontinuous) kinetic transition in the Ziff-Gulari-Barshad model of catalytic surface reaction. The average time for the transition to take place, as well as both the spinodal and transition points, are clearly found by this method.Comment: 12 pages, 10 figure