The Brumer-Stark Conjecture and its Refinements

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This project concerns algebraic number theory, a branch of mathematics that aims to study properties of the basic number systems arising from roots of polynomials (called number fields). Number theorists are interested in classifying number fields whose symmetry groups (called Galois groups) have the commutative property, and in producing formulas to generate these special number fields. Modern methods have demonstrated the connection between number fields and certain associated functions called L-functions, whose values encode many of the most important conjectures in number theory. The principal investigator, Dr. Samit Dasgupta, has made important progress on these topics in recent work, and the current proposal aims to push further in this direction. Dr. Dasgupta also plans to continue and expand his activities to disseminate mathematics to students and academics of all age groups and career stages. Dr. Dasgupta gives expository lectures for undergraduates in various math clubs, teaches minicourses for graduate students, is involved in graduate and postdoctoral advising, is involved in local conference organizing, and is on the editorial board of several journals. All these activities connect to Dr. Dasgupta’s goal to promote mathematics holistically in society, with a particular view toward supporting various groups that have been traditionally underrepresented. More technically, Dr. Dasgupta’s work is motivated by two central problems in modern algebraic number theory: the expression of special values of classical and p-adic L-functions as regulators of algebraic objects, and the generation of abelian extensions of number fields through analytic means intrinsic to the ground field, as codified in Hilbert's 12th problem. Dr. Dasgupta’s prior work has made significant progress on the Brumer-Stark Conjecture, the Gross-Stark Conjecture, and the explicit analytic construction of class fields of totally real fields. Dr. Dasgupta will continue his explorations in this direction with five specific questions on the connections between Stark units, L-functions, modular forms, and Galois representations. All these projects will advance our knowledge in a significant way on the relationship between special values of L-functions and associated algebraic objects. Firstly, he will complete the proof of the Brumer-Stark conjecture by handling the localization at p=2. Next, he will extend his work with Kakde to prove the Equivariant Tamagawa Number Conjecture for the minus part of CM abelian extensions of totally real fields, including at the prime 2. In joint work with Spiess, Dr. Dasgupta will prove their joint conjecture on the characteristic polynomial of Gross's regulator matrix. Separately, he will work with Darmon and Charollois on expanding the strategy of Darmon, Vonk, and Pozzi for real quadratic fields to give a purely p-adic analytic proof of Dr. Dasgupta's explicit analytic formula for Brumer-Stark units over arbitrary totally real fields. Dr. Dasgupta will work with Victor Rotger to study a conjecture of Harris and Venkatesh relating the derived Hecke operators defined by Venkatesh to Stark units in the Galois extension cut out by the adjoint of the Galois representation attached to weight one forms.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.