Is the full susceptibility of the square-lattice Ising model a differentially algebraic function?

Self Cite

Abstract. We show that non-linear Schwarzian differential equations emerging from covariance symmetry conditions imposed on linear differential operators with hypergeometric function solutions can be generalized to arbitrary order linear differential operators with polynomial coefficients having selected differential Galois groups. For order three and order four linear differential operators we show that this pullback invariance up to conjugation eventually reduces to symmetric powers of an underlying order-two operator. We give, precisely, the conditions to have modular correspondences solutions for such Schwarzian differential equations, which was an open question in a previous paper. We analyze in detail a pullbacked hypergeometric example generalizing modular forms, that ushers a pullback invariance up to operator homomorphisms. We expect this new concept to be well-suited in physics and enumerative combinatorics. We finally consider the more general problem of the equivalence of two different orderfour linear differential Calabi-Yau operators up to pullbacks and conjugation, and clarify the cases where they have the same Yukawa couplings.

Section: Introductionsupporting

confidence: 53%

Section: Order-four Linear Differential Operatorsmentioning

confidence: 99%

Section: Calabi-yau Condition (Exterior Square)mentioning

confidence: 99%

Section: Symmetric Calabi-yau Conditionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Schwarzian conditions for linear differential operators with selected differential Galois groups

Abdelaziz¹,

Maillard²

2017

Self Cite

Modular forms, Schwarzian conditions, and symmetries of differential equations in physics

Abdelaziz¹,

Maillard²

2017

Self Cite

110

Abstract.We give examples of infinite order rational transformations that leave linear differential equations covariant. These examples are non-trivial yet simple enough illustrations of exact representations of the renormalization group. We first illustrate covariance properties on order-two linear differential operators associated with identities relating the same 2 F 1 hypergeometric function with different rational pullbacks. These rational transformations are solutions of a differentially algebraic equation that already emerged in a paper by Casale on the Galoisian envelopes. We provide two new and more general results of the previous covariance by rational functions: a new Heun function example and a higher genus 2 F 1 hypergeometric function example. We then focus on identities relating the same 2 F 1 hypergeometric function with two different algebraic pullback transformations: such remarkable identities correspond to modular forms, the algebraic transformations being solution of another differentially algebraic Schwarzian equation that also emerged in Casale's paper. Further, we show that the first differentially algebraic equation can be seen as a subcase of the last Schwarzian differential condition, the restriction corresponding to a factorization condition of some associated order-two linear differential operator. Finally, we also explore generalizations of these results, for instance, to 3 F 2 , hypergeometric functions, and show that one just reduces to the previous 2 F 1 cases through a Clausen identity. The question of the reduction of these Schwarzian conditions to modular correspondences remains an open question. In a 2 F 1 hypergeometric framework the Schwarzian condition encapsulates all the modular forms and modular equations of the theory of elliptic curves, but these two conditions are actually richer than elliptic curves or 2 F 1 hypergeometric functions, as can be seen on the Heun and higher genus example. This work is a strong incentive to develop more differentially algebraic symmetry analysis in physics.

On Christol’s conjecture

Abdelaziz¹,

Koutschan

Maillard³

2020

We show that the unresolved examples of Christol's conjecture 3 F 2 ([2/9, 5/9, 8/9], [2/3, 1], x) and 3 F 2 ([1/9, 4/9, 7/9], [1/3, 1], x), are indeed diagonals of rational functions.We also show that other 3 F 2 and 4 F 3 unresolved examples of Christol's conjecture are diagonals of rational functions. Finally we give two arguments that show that it is likely that the 3 F 2 ([1/9, 4/9, 5/9], [1/3, 1], 27 · x) function is a diagonal of a rational function.