Relevant Degree Programs
Graduate Student Supervision
Doctoral Student Supervision (Jan 2008 - Mar 2019)
The arithmetic function λ(n) is the exponent of the cyclic group (Z/nZ)^x. The k-th iterate of λ(n) is denoted by λk(n) In this work we will show the normal order for log(n/λk(n)) is (loglog n)k⁻¹}(logloglog n)/(k-1)! . Second, we establish a similar normal order for other iterate involving a combination of λ(n) and Φ(n). Lastly, define L(n) to be the smallest k such that λ_k(n)=1. We determine new upper and lower bounds for L(n) and conjecture a normal order.
We study questions in three arithmetic settings, each of which carries aspects of random-like behaviour.In the setting of arithmetic functions, we establish mild conditions under which the tuple of multiplicative functions [f₁, f₂, …, f_d ], evaluated at d consecutive integers n+1, …, n+d, closely approximates points in R^d for a positive proportion of n; we obtain a further generalization which allows these functions to be composed with various arithmetic progressions.Secondly, we examine the eigenvalues of random integer matrices, showing that most matrices have no rational eigenvalues; we also identify the precise distributions of both real and rational eigenvalues in the 2 × 2 case. Finally, we consider the set S(k) of numbers represented by the quadratic form x² + ky², showing that it contains infinitely many strings of five consecutive integers under many choices of k; we also characterize exactly which numbers can appear as the difference of two consecutive values in S(k).
In this work we will consider several questions concerning the asymptoticnature of arithmetic functions. First, we conduct a finer analysis on the behaviorof λ(Euler's totient function(n)) in relation to λ(λ(n)), proving that log(λ(Euler's totient function(n))/λ(λ(n)))is asymptotic to (log log n)(log log log n)for almost all n. Second, we establishan asymptotic formula for sums of a generalized divisor function on theGaussian numbers. And third, for complex-valued multiplicative functionsthat are suffciently close to 1 on the primes and bounded on prime powers,we determine the average value over a short interval x
Master's Student Supervision (2010-2017)
The class number problem is one of the central open problems of algebraic number theory. It has long been known that there are only finitely many imaginary quadratic fields of class number one, and the full list of such fields is given by the Stark-Heegner theorem, but the corresponding problem for real quadratic fields is still open. It is conjectured that infinitely many real quadratic fields have class number one but at present it is still unknown even whether infinitely many algebraic number fields have class number one. This thesis reviews the relevant work that has been done on this problem in the last several decades. It is primarily concerned with a heuristic model of the sequence of real quadratic class groups called the Cohen-Lenstra heuristics, since this appears to offer the best hope of potentially solving the class number problem. The work of several other people who have put forward interpretations of the Cohen-Lenstra heuristics in other contexts, or who have generalized the heuristics, is also reviewed.
In this thesis we extend two important theorems in analytic prime number theory to a the setting of Beurling primes, namely The Erdős–Kac theorem and a theorem of Sathe and Selberg. The Erdős–Kac theoremasserts that the number of prime factors that divide an integer n is, in some sense, normally distributed with mean log log n and variancelog log n. Sathe proved and Selberg substantially refined a formula for the counting function of products of k primes with some uniformity on k. A set of Beurling primes is any countable multiset of the reals with elements that tend towards infinity. The set of Beurling primes has a corresponding multiset of Beurling integers formed by all finite products of Beurling primes. We assume that the Beurling integer counting function is approximately linear with varying conditions on the error term in order to prove the stated results. An interesting example of a set of Beurling primes is the set of norms of prime ideals of the ring of integers of a number field. Recently, Granville and Soundararajan have developed a particularly simple proof of the Erdős–Kac theorem which we follow in this thesis. For extending the theorem of Selberg and Sathe much more analytic machinery is needed.