A study of how the student and exchange visa information system influences the influx and study of graduate international students in science and engineering in the U.S.

Thesis (Ed.D.)--Boston UniversityThe influx of international graduate students in science and engineering to the U.S. has changed since the terrorist attacks of September 11, 2001. The implementation of the Student and Exchange Visitor Information System (SEVIS) and related F-1 visa policies have required a higher level of scrutiny of the student visa procedures, and introduced strict student monitoring policies and measures. In addition, the SEVIS monitoring and compliance system has altered the operation of international student service offices, affected the students they serve, and the operation of the universities enrolling international students. This study investigated the effects of SEVIS on graduate programs in science and engineering and their students. Information was gathered from respondents from the 60 universities having the highest population of intemational students in these fields, according to NSF. Respondents included department administrators, admissions officials, and SEVIS professionals. Data V111 were collected from 75 on-line survey respondents and in 21 semi-structured interviews. The results of this study suggest that many international students are negatively affected by SEVIS, impacting their ability to remain in-status and to understand how the system works. To counter this, department administrators, SEVIS professionals, and student advisors have increased their level of support for these students, providing them guidance on how to remain in-status and how to improve their social and academic experience in the United States. As a result, relatively few international students are deported for falling out-of-status in SEVIS. The data also made clear that program administrators and admissions officials have little knowledge about SEVIS, F -1 visa policies, and their influence on international enrollments. Finally, this study provided evidence of an increased workload for international student advisors and SEVIS professionals. Universities have had to hire additional staff, increase their information technology investment in linking home-grown student service systems with SEVIS, and proactively anticipate any hurdles that international students may have and resolve them as expeditiously as possible.2031-01-0

Hidden Beauty in Multiloop Amplitudes

Planar L-loop maximally helicity violating amplitudes in N = 4 supersymmetric Yang-Mills theory are believed to possess the remarkable property of satisfying iteration relations in L. We propose a simple new method for studying the iteration relations for four-particle amplitudes which involves the use of certain linear differential operators and eliminates the need to fully evaluate any loop integrals. We carry out this procedure in explicit detail for the two-loop amplitude and argue that this method can be used to prove the iteration relations to all loops up to polynomials in logarithms.Comment: 21 pages, harvmac; v2: minor change

Coin Tossing as a Billiard Problem

We demonstrate that the free motion of any two-dimensional rigid body colliding elastically with two parallel, flat walls is equivalent to a billiard system. Using this equivalence, we analyze the integrable and chaotic properties of this new class of billiards. This provides a demonstration that coin tossing, the prototypical example of an independent random process, is a completely chaotic (Bernoulli) problem. The related question of which billiard geometries can be represented as rigid body systems is examined.Comment: 16 pages, LaTe

The Inverse Scattering Method, Lie-Backlund Transformations and Solitons for Low-energy Effective Field Equations of 5D String Theory

In the framework of the 5D low-energy effective field theory of the heterotic string with no vector fields excited, we combine two non-linear methods in order to construct a solitonic field configuration. We first apply the inverse scattering method on a trivial vacuum solution and obtain an stationary axisymmetric two-soliton configuration consisting of a massless gravitational field coupled to a non-trivial chargeless dilaton and to an axion field endowed with charge. The implementation of this method was done following a scheme previously proposed by Yurova. We also show that within this scheme, is not possible to get massive gravitational solitons at all. We then apply a non-linear Lie-Backlund matrix transformation of Ehlers type on this massless solution and get a massive rotating axisymmetric gravitational soliton coupled to axion and dilaton fields endowed with charges. We study as well some physical properties of the constructed massless and massive solitons and discuss on the effect of the generalized solution generating technique on the seed solution and its further generalizations.Comment: 17 pages in latex, changed title, improved text, added reference

On the Strong Coupling Scaling Dimension of High Spin Operators

We give an exact analytic solution of the strong coupling limit of the integral equation which was recently proposed to describe the universal scaling function of high spin operators in N = 4 gauge theory. The solution agrees with the prediction from string theory, confirms the earlier numerical analysis and provides a basis for developing a systematic perturbation theory around strong coupling.Comment: 26 pages, 2 figure

Higher Order Evaluation of the Critical Temperature for Interacting Homogeneous Dilute Bose Gases

We use the nonperturbative linear \delta expansion method to evaluate analytically the coefficients c_1 and c_2^{\prime \prime} which appear in the expansion for the transition temperature for a dilute, homogeneous, three dimensional Bose gas given by T_c= T_0 \{1 + c_1 a n^{1/3} + [ c_2^{\prime} \ln(a n^{1/3}) +c_2^{\prime \prime} ] a^2 n^{2/3} + {\cal O} (a^3 n)\}, where T_0 is the result for an ideal gas, a is the s-wave scattering length and n is the number density. In a previous work the same method has been used to evaluate c_1 to order-\delta^2 with the result c_1= 3.06. Here, we push the calculation to the next two orders obtaining c_1=2.45 at order-\delta^3 and c_1=1.48 at order-\delta^4. Analysing the topology of the graphs involved we discuss how our results relate to other nonperturbative analytical methods such as the self-consistent resummation and the 1/N approximations. At the same orders we obtain c_2^{\prime\prime}=101.4, c_2^{\prime \prime}=98.2 and c_2^{\prime \prime}=82.9. Our analytical results seem to support the recent Monte Carlo estimates c_1=1.32 \pm 0.02 and c_2^{\prime \prime}= 75.7 \pm 0.4.Comment: 29 pages, 3 eps figures. Minor changes, one reference added. Version in press Physical Review A (2002

Asymptotically Improved Convergence of Optimized Perturbation Theory in the Bose-Einstein Condensation Problem

We investigate the convergence properties of optimized perturbation theory, or linear $\delta$ expansion (LDE), within the context of finite temperature phase transitions. Our results prove the reliability of these methods, recently employed in the determination of the critical temperature T_c for a system of weakly interacting homogeneous dilute Bose gas. We carry out the explicit LDE optimized calculations and also the infrared analysis of the relevant quantities involved in the determination of $T_c$ in the large-N limit, when the relevant effective static action describing the system is extended to O(N) symmetry. Then, using an efficient resummation method, we show how the LDE can exactly reproduce the known large-N result for $T_c$ already at the first non-trivial order. Next, we consider the finite N=2 case where, using similar resummation techniques, we improve the analytical results for the nonperturbative terms involved in the expression for the critical temperature allowing comparison with recent Monte Carlo estimates of them. To illustrate the method we have considered a simple geometric series showing how the procedure as a whole works consistently in a general case.Comment: 38 pages, 3 eps figures, Revtex4. Final version in press Phys. Rev.