The optimal P3M algorithm for computing electrostatic energies in periodic systems

We optimize Hockney and Eastwood's Particle-Particle Particle-Mesh (P3M) algorithm to achieve maximal accuracy in the electrostatic energies (instead of forces) in 3D periodic charged systems. To this end we construct an optimal influence function that minimizes the RMS errors in the energies. As a by-product we derive a new real-space cut-off correction term, give a transparent derivation of the systematic errors in terms of Madelung energies, and provide an accurate analytical estimate for the RMS error of the energies. This error estimate is a useful indicator of the accuracy of the computed energies, and allows an easy and precise determination of the optimal values of the various parameters in the algorithm (Ewald splitting parameter, mesh size and charge assignment order).Comment: 31 pages, 3 figure

Students Without Documentation: Context and Solutions to Navigating Systemic Barriers in Higher Education

This professional project includes five chapters, with the fourth chapter being a draft of an article, which is the culmination of this professional project. This professional project identified gaps in past literature and examined institutional barriers that impact access to higher education institutions for students without documentation (SWD) at the state and federal levels. The draft of the article for this project will explore the policy and sociopolitical context that impacts SWD as they navigate higher education. Further, the article draft suggests ways to support SWD informed by past literature. The social factors that impact SWD and will be discussed are the following: social capital, mental health, misconceptions, and invisibility. Lastly, the draft of the article concludes with an action plan for educational professionals and relevant ways to advocate for SWD to help them thrive in higher education and life. The importance of a long-term solution at the federal level for immigration reform to increase access to higher education institutions for SWD will be emphasized. Keywords: immigration, students without documentation, DACA, DREAMers, higher education

Magneto-elastic oscillations of neutron stars: exploring different magnetic field configurations

We study magneto-elastic oscillations of highly magnetized neutron stars (magnetars) which have been proposed as an explanation for the quasi-periodic oscillations (QPOs) appearing in the decaying tail of the giant flares of soft gamma-ray repeaters (SGRs). We extend previous studies by investigating various magnetic field configurations, computing the Alfv\'en spectrum in each case and performing magneto-elastic simulations for a selected number of models. By identifying the observed frequencies of 28 Hz (SGR 1900+14) and 30 Hz (SGR 1806-20) with the fundamental Alfv\'en QPOs, we estimate the required surface magnetic field strength. For the magnetic field configurations investigated (dipole-like poloidal, mixed toroidal-poloidal with a dipole-like poloidal component and a toroidal field confined to the region of field lines closing inside the star, and for poloidal fields with an additional quadrupole-like component) the estimated dipole spin-down magnetic fields are between 8x10^14 G and 4x10^15 G, in broad agreement with spin-down estimates for the SGR sources producing giant flares. A number of these models exhibit a rich Alfv\'en continuum revealing new turning points which can produce QPOs. This allows one to explain most of the observed QPO frequencies as associated with magneto-elastic QPOs. In particular, we construct a possible configuration with two turning points in the spectrum which can explain all observed QPOs of SGR 1900+14. Finally, we find that magnetic field configurations which are entirely confined in the crust (if the core is assumed to be a type I superconductor) are not favoured, due to difficulties in explaining the lowest observed QPO frequencies (f<30 Hz).Comment: 21 pages, 16 figures, 6 tables, matched to version accepted by MNRAS with extended comparison/discussion to previous wor

Lee-Carter method for forecasting mortality for Peruvian Population

In this article, we have modeled mortality rates of Peruvian female and male populations during the period&nbsp;of 1950-2017 using the two-factor Lee-Carter (LC) model. The stochastic mortality model was introduced&nbsp;by Lee and Carter (1992) and has been used by many authors for fitting and forecasting the human mortality&nbsp;rates. The Singular Value Decomposition (SVD) approach is used for estimation of the parameters of the&nbsp;LC model. Utilizing the best fitted auto regressive integrated moving average (ARIMA) model we forecast&nbsp;the values of the time dependent parameter of the LC model for the next thirty years. The forecasted values&nbsp;of life expectancy at different age group with 95% confidence intervals are also reported for the next thirty&nbsp; years. In this research we use the data, obtained from the Peruvian National Institute of Statistics (INEI). &nbsp;In this article, we have modeled mortality rates of Peruvian female and male populations during the period&nbsp;of 1950-2017 using the two-factor Lee-Carter (LC) model. The stochastic mortality model was introduced&nbsp;by Lee and Carter (1992) and has been used by many authors for fitting and forecasting the human mortality&nbsp;rates. The Singular Value Decomposition (SVD) approach is used for estimation of the parameters of the&nbsp;LC model. Utilizing the best fitted auto regressive integrated moving average (ARIMA) model we forecast&nbsp;the values of the time dependent parameter of the LC model for the next thirty years. The forecasted values&nbsp;of life expectancy at different age group with 95% confidence intervals are also reported for the next thirty&nbsp; years. In this research we use the data, obtained from the Peruvian National Institute of Statistics (INEI). &nbsp

Lee-Carter method for forecasting mortality for Peruvian Population

In this article, we have modeled mortality rates of Peruvian female and male populations during the period of 1950-2017 using the Lee-Carter (LC) model. The stochastic mortality model was introduced by Lee and Carter (1992) and has been used by many authors for fitting and forecasting the human mortality rates. The Singular Value Decomposition (SVD) approach is used for estimation of the parameters of the LC model. Utilizing the best fitted auto regressive integrated moving average (ARIMA) model we forecast the values of the time dependent parameter of the LC model for the next thirty years. The forecasted values of life expectancy at different age group with $95\%$ confidence intervals are also reported for the next thirty years. In this research we use the data, obtained from the Peruvian National Institute of Statistics (INEI).Comment: 16 pages, 6 figure