Sumit BanikResearch

Feynman integrals, effective field theories and physics beyond the Standard Model.

The tour, slide by slide

    A physical law must possess mathematical beauty.

    P. A. M. Dirac, 1955

    Research domains

    Mathematical physics

    Multiple Mellin-Barnes integrals, GKZ hypergeometric systems and multivariate hypergeometric functions, with series representations from conic hulls and triangulations, analytic continuation, high-precision evaluation and the method of brackets.

    Mellin-Barnes integrals · GKZ systems · Hypergeometric functions
    17 papers

    Feynman integrals

    Analytic and numerical evaluation of multi-loop, multi-scale Feynman integrals, such as conformal hexagon, double box and one-loop n-point integrals, sunset integrals in chiral perturbation theory, and their ε-expansion in dimensional regularization.

    Multi-loop · Multi-scale · Conformal integrals
    15 papers

    Multi-Higgs physics

    Extended scalar sectors such as the 2HDM, the N2HDM and Higgs triplets, confronted with the di-photon excesses near 95 and 152 GeV at the LHC, differential top-quark distributions, the W mass and electric dipole moments.

    2HDM · Higgs triplets · LHC excesses
    11 papers

    Computational tools

    Open-source Mathematica packages: MBConicHulls for multiple Mellin-Barnes integrals, FeynGKZ for Feynman integrals via GKZ systems, and HyperPrecision for multivariate hypergeometric functions.

    Mathematica · Computer algebra · High precision
    Three packages and a library

    Effective field theory

    The Standard Model effective field theory and the renormalization group: two-loop anomalous dimensions of baryon-number-violating operators for proton decay, two-loop running with scalar leptoquarks, and the summation of large logarithms.

    SMEFT · RG evolution · Proton decay
    3 papers

    Exotic particles

    Scalar leptoquarks beyond the Standard Model: two-loop renormalization group evolution, the unification of gauge and Yukawa couplings, and one-loop matching onto the SMEFT.

    Leptoquarks · Unification · SMEFT matching
    2 papers

    Selected work

    A map of the papers

    Each dot is one of the 30 papers, placed by the words its title and abstract share with the others, so that papers on the same subject sit close together. A line joins each paper to the three closest to it.

    One integral, two series

    Closing the contour of a Mellin-Barnes integral to the right or to the left picks up different poles, and gives a different series for the same function. Each series converges in a region of its own, and each is the analytic continuation of the other. Here is the integral of the slide What is a Mellin-Barnes integral? in the tour above, with the number of terms on a slider.

    I(x) = ∫ dz/2πi (−x)z Γ(−z) Γ(−½ + z) = −2√π (1 − x)½

    30
    • Closing to the right, on the poles of Γ(−z): Σn Γ(n − ½) xn/n!, which converges for |x| ≤ 1
    • Closing to the left, on the poles of Γ(−½ + z): (−x)½ Σn Γ(n − ½) x−n/n!, which converges for |x| ≥ 1
    • The function itself, −2√π (1 − x)½
    The radius of the series in x is set by the branch point of (1 − x)½ at x = 1. On the real line the two regions meet at x = −1, where the two series are the same series term by term. With more integration variables there are many more ways to close the contours. The two-fold integral of the Appell function F1 already has five series representations, whose regions of convergence tile the plane of |u1| and |u2| (Phys. Rev. Lett. 127, 151601), and the nine-fold integral of the conformal hexagon has 194160 (Phys. Rev. D 110, 036002). MBConicHulls derives them automatically.

    Software

    The open-source Mathematica packages and the library that came out of this research, developed with my collaborators. Each one opens on the Software page, with its versions, requirements and installation.

    Contact

    Feel free to get in touch. I am always happy to hear from you.

    Send an email or find me on INSPIRE, GitHub and LinkedIn.

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