Javad Komijani


Last Name

Komijani

First Name

Javad

ORCID

0000-0002-6943-8735

Organisational unit

09738 - Krstic Marinkovic, Marina / Krstic Marinkovic, Marina

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2021 - 20258
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Publications 1 - 8 of 8
  • Preparing for MUonE experiment—what can we learn from lattice and dispersive data?
    Item type: Conference Paper
    Komijani, Javad; Marinkovic, Marina (2022)
    Mini-Proceedings of the STRONG2020 Virtual Workshop on ''Space-like and Time-like determination of the Hadronic Leading Order contribution to the Muon g−2"
  • A first look at the HVP from QCD and QCD+QED with C* boundary conditions II
    Item type: Other Conference Item
    Altherr, Anian; Gruber, Roman; Patella, Agostino; et al. (2022)
    The 39th International Symposium on Lattice Field Theory (Lattice 2022): Book of Abstracts
  • Addendum: Painleve transcendents and PT-symmetric Hamiltonians (2015 J. Phys. A: Math. Theor. 48 475202)
    Item type: Journal Article
    Bender, Carl M.; Komijani, Javad (2022)
    Journal of Physics A: Mathematical and Theoretical
    This paper is an Addendum to reference Bender and Komijani (2015 J. Phys. A: Math. Theor 48 475202) (which stems from an earlier paper Bender et al (2014 J. Phys. A: Math. Theor 47 235204)), where it was demonstrated that unstable separatrix solutions to the Painleve equations I and II are determined by PT-symmetric Hamiltonians. Here, unstable separatrix solutions of the fourth Painleve transcendent are studied numerically and analytically. It is shown that for a fixed initial value such as y(0) = 1 a discrete set of initial slopes y'(0) = b(n) give rise to separatrix solutions. Similarly, for a fixed initial slope such as y'(0) = 0 a discrete set of initial values y(0) = c(n) give rise to separatrix solutions. For Painleve IV the large-n asymptotic behavior of b(n) is b(n) similar to B(IV)n(3/4) and that of c(n) is c(n) similar to C(IV)n(1/2). The constants B-IV and C-IV are determined both numerically and analytically. The analytical values of these constants are found by reducing the nonlinear Painleve IV equation to the linear eigenvalue equation for the sextic PT-symmetric Hamiltonian H = 1/2p(2) + 1/8x(6).
  • Comparing QCD+QED via full simulation versus the RM123 method: U-spin window contribution to a_{µ}ᴴⱽᴾ
    Item type: Journal Article
    Altherr, Anian; Campos, Isabel; Cotellucci, Alessandro; et al. (2025)
    Journal of High Energy Physics
    Electromagnetic corrections to hadronic vacuum polarization contribute significantly to the uncertainty of the Standard Model prediction of the muon anomaly, which poses conceptual and numerical challenges for ab initio lattice determinations. In this study, we compute the non-singlet contribution from intermediate Euclidean current separations in quantum chromo- and electrodynamics (QCD+QED) using C⋆ boundary conditions in two ways: either non-perturbatively by sampling the joint probability distribution directly or by perturbatively expanding from an isospin-symmetric theory. This allows us to compare the predictions and their uncertainties at a fixed lattice spacing and volume, including fully the sea quarks effects in both cases. Treating carefully the uncertainty due to tuning to the same renormalized theory with Nf = 1 + 2 + 1 quarks, albeit with unphysical masses, we find it advantageous to simulate the full QCD+QED distribution given a fixed number of samples. This study lays the ground-work for further applications of C⋆ boundary conditions to study QCD+QED at the physical point, essential for the next generation of precision tests of the Standard Model.
  • Strange and charm contributions to the HVP from C* boundary conditions
    Item type: Conference Paper
    Tavella, Paola; Altherr, Anian; Bushnaq, Lucius; et al. (2023)
    PoS: Proceedings of Science ~ Proceedings of The 39th International Symposium on Lattice Field Theory (LATTICE2022)
  • Hadronic vacuum polarization with C* boundary conditions
    Item type: Conference Paper
    Altherr, Anian; Gruber, Roman; Bushnaq, Lucius; et al. (2023)
    PoS: Proceedings of Science ~ Proceedings of The 39th International Symposium on Lattice Field Theory (LATTICE2022)
  • First-order nonlinear eigenvalue problems involving functions of a general oscillatory behavior
    Item type: Journal Article
    Komijani, Javad (2021)
    Journal of Physics A: Mathematical and Theoretical
    Eigenvalue problems arise in many areas of physics, from solving a classical electromagnetic problem to calculating the quantum bound states of the hydrogen atom. In textbooks, eigenvalue problems are defined for linear problems, particularly linear differential equations such as time-independent Schrödinger equations. Eigenfunctions of such problems exhibit several standard features independent of the form of the underlying equations. As discussed in Bender et al (2014 J. Phys.A: Math. Theor. 47 235204), separatrices of nonlinear differential equations share some of these features. In this sense, they can be considered eigenfunctions of nonlinear differential equations, and the quantized initial conditions that give rise to the separatrices can be interpreted as eigenvalues.We introduce a first-order nonlinear eigenvalue problem involving a general class of functions and obtain the large-eigenvalue limit by reducing it to a random walk problem on a half-line. The introduced general class of functions covers many special functions such as the Bessel and Airy functions, which are themselves solutions of second-order differential equations. For instance, in a special case involving the Bessel functions of the first kind, i.e. for y'(x) = Jv (xy), we show that the eigenvalues asymptotically grow as 241/42n1/4.We also introduce and discuss nonlinear eigenvalue problems involving the reciprocal gamma and the Riemann zeta functions, which are not solutions to simple differential equations. With the reciprocal gamma function, i.e. for y'(x) = 1/Γ(-xy), we show that the nth eigenvalue grows factorially fast as √ (1 - 2n)/Γ(r2n-1), where rk is the kth root of the digamma function.
  • Generative models for scalar field theories: how to deal with poor scaling?
    Item type: Conference Paper
    Komijani, Javad; Marinkovic, Marina (2023)
    PoS: Proceedings of Science ~ Proceedings of The 39th International Symposium on Lattice Field Theory (LATTICE2022)
    Generative models, such as the method of normalizing flows, have been suggested as alternatives to the standard algorithms for generating lattice gauge field configurations. Studies with the method of normalizing flows demonstrate the proof of principle for simple models in two dimensions. However, further studies indicate that the training cost can be, in general, very high for large lattices. The poor scaling traits of current models indicate that moderate-size networks cannot efficiently handle the inherently multi-scale aspects of the problem, especially around critical points. We explore current models with limited acceptance rates for large lattices and examine new architectures inspired by effective field theories to improve scaling traits. We also discuss alternative ways of handling poor acceptance rates for large lattices.
Publications 1 - 8 of 8