Publications

Order by: publication date number of citations

• The pion-photon transition form factor at two loops in QCD

  Jing Gao, Tobias Huber, Yao Ji, Yu-Ming Wang

  SciPost Phys. Proc. 7, 022 (2022) · published 21 June 2022 | Toggle abstract · pdf

  We report on the fully analytic calculation of the leading-power contribution to the photon-pion transition form factor $\gamma \, \gamma^{\ast} \to \pi^0$ at two loops in QCD. The applied techniques are based on hard-collinear factorization, together with modern multi-loop methods. We focus both, on the technical details such as the treatment of evanescent operators, and the phenomenological implications. Our results indicate that the two-loop correction is numerically comparable to the one-loop effect in the same kinematic domain. We also demonstrate that our results will play a key role in disentangling various models for the twist-two pion distribution amplitude thanks to the envisaged precision at Belle II.

  1 citation

• Constraints on heavy dark matter annihilation and decay from electron and positron cosmic ray spectra

  Holger Motz

  SciPost Phys. Proc. 12, 035 (2023) · published 4 July 2023 | Toggle abstract · pdf

  Annihilation or decay of dark matter (DM) could contribute to the electron and positron cosmic-ray flux, allowing for constraints on DM parameters from its measurement. CALET is directly measuring the energy spectrum of electron+positron cosmic rays up into the TeV region most important for studying heavy DM, while AMS-02 provides a positron-only spectrum below the TeV range. Limits on DM annihilation and decay well into the TeV mass range have been derived from a combined analysis of both data-sets with an astrophysical background model including pulsars as the origin of the positron excess and individual nearby supernova remnant sources.

  1 citation

• A range three elliptic deformation of the Hubbard model

  Marius de Leeuw, Chiara Paletta, Balázs Pozsgay

  SciPost Phys. 15, 071 (2023) · published 28 August 2023 | Toggle abstract · pdf

  In this paper we present a new integrable deformation of the Hubbard model. Our deformation gives rise to a range 3 interaction term in the Hamiltonian which does not preserve spin or particle number. This is the first non-trivial medium range deformation of the Hubbard model that is integrable. Our model can be mapped to a new integrable nearest-neighbour model via a duality transformation. The resulting nearest-neighbour model also breaks spin conservation. We compute the $R$-matrices for our models, and find that there is a very unusual dependence on the spectral parameters in terms of the elliptic amplitude.

  1 citation

• Quenched random mass disorder in the large N theory of vector bosons

  Han Ma

  SciPost Phys. 14, 039 (2023) · published 17 March 2023 | Toggle abstract · pdf

  We study the critical bosonic O(N) vector model with quenched random mass disorder in the large N limit. Due to the replicated action which is sometimes not bounded from below, we avoid the replica trick and adopt a traditional approach to directly compute the disorder averaged physical observables. At $N=\infty$, we can exactly solve the disordered model. The resulting low energy behavior can be described by two scale invariant theories, one of which has an intrinsic scale. At finite $N$, we find that the previously proposed attractive disordered fixed point at $d=2$ continues to exist at $d=2+\epsilon$ spatial dimensions. We also studied the system in the $3<d<4$ spatial dimensions where the disorder is relevant at the Gaussian fixed point. However, no physical attractive fixed point is found right below four spatial dimensions. Nevertheless, the stable fixed point at $2+\epsilon$ dimensions can still survive at $d=3$ where the system has experimental realizations. Some critical exponents are predicted in order to be checked by future numerics and experiments.

  1 citation

• Generalized parton distribution functions of $\rho$ meson

  Baodong Sun, Yubing Dong

  SciPost Phys. Proc. 3, 014 (2020) · published 25 February 2020 | Toggle abstract · pdf

  We report our recent calculations for the generalized parton distribution functions of the $\rho$ meson with the help of a light-front constituent quark model. The electromagnetic form factors and structure functions of the system are given. Moreover, we also show our results for its gravitational form factors (or energy-momentum tensor form factors) and for other mechanical properties, like its mass distributions, pressures, share-forces, and $D-$term.

  1 citation

• The inheritance of energy conditions: Revisiting no-go theorems in string compactifications

  Heliudson Bernardo, Suddhasattwa Brahma, Mir Mehedi Faruk

  SciPost Phys. 15, 225 (2023) · published 5 December 2023 | Toggle abstract · pdf

  One of the fundamental challenges in string theory is to derive realistic four-dimensional cosmological backgrounds from it despite strict consistency conditions that constrain its possible low-energy backgrounds. In this work, we focus on energy conditions as covariant and background-independent consistency requirements in order to classify possible backgrounds coming from low-energy string theory in two steps. Firstly, we show how supergravity actions obey many relevant energy conditions under some reasonable assumptions. Remarkably, we find that the energy conditions are satisfied even in the presence of objects which individually violate them due to the tadpole cancellation condition. Thereafter, we list a set of conditions for a higher-dimensional energy condition to imply the corresponding lower-dimensional one, thereby categorizing the allowed low-energy solutions. As for any no-go theorem, our aim is to highlight the assumptions that must be circumvented for deriving four-dimensional spacetimes that necessarily violate these energy conditions, with emphasis on cosmological backgrounds.

  1 citation

• An accurate allowance for initial and final state interactions in the treatment of the alpha-alpha Bremsstrahlung

  Adam M. Arslanaliev, Aleksandr V. Shebeko

  SciPost Phys. Proc. 3, 042 (2020) · published 27 February 2020 | Toggle abstract · pdf

  The alpha-alpha bremsstrahlung is studied using the generalization of the Siegert theorem. The corresponding amplitude is written in the gauge invariant form. Special attention is paid to taking into account the Coulomb interaction. Some correlation function is found and its dependence on the strong interaction is discussed.

  1 citation

• Integrable deformations of superintegrable quantum circuits

  Tamás Gombor, Balázs Pozsgay

  SciPost Phys. 16, 114 (2024) · published 26 April 2024 | Toggle abstract · pdf

  Superintegrable models are very special dynamical systems: they possess more conservation laws than what is necessary for integrability. This severely constrains their dynamical processes, and it often leads to their exact solvability, even in non-equilibrium situations. In this paper we consider special Hamiltonian deformations of superintegrable quantum circuits. The deformations break superintegrability, but they preserve integrability. We focus on a selection of concrete models and show that for each model there is an (at least) one parameter family of integrable deformations. Our most interesting example is the so-called Rule54 model. We show that the model is compatible with a one parameter family of Yang-Baxter integrable spin chains with six-site interaction. Therefore, the Rule54 model does not have a unique integrability structure, instead it lies at the intersection of a family of quantum integrable models.

  1 citation

• Seven Études on dynamical Keldysh model

  Dmitri V. Efremov, Mikhail N. Kiselev

  SciPost Phys. Lect. Notes 65 (2022) · published 6 December 2022 | Toggle abstract · pdf

  We present a comprehensive pedagogical discussion of a family of models describing the propagation of a single particle in a multicomponent non-Markovian Gaussian random field. We report some exact results for single-particle Green's functions, self-energy, vertex part and T-matrix. These results are based on a closed form solution of the Dyson equation combined with the Ward identity. Analytical properties of the solution are discussed. Further we describe the combinatorics of the Feynman diagrams for the Green's function and the skeleton diagrams for the self-energy and vertex, using recurrence relations between the Taylor expansion coefficients of the self-energy. Asymptotically exact equations for the number of skeleton diagrams in the limit of large $N$ are derived. Finally, we consider possible realizations of a multicomponent Gaussian random potential in quantum transport via complex quantum dot experiments.

  1 citation

• Attenuation of cosmic-ray up-scattered dark matter

  Helena Kolesova

  SciPost Phys. Proc. 12, 055 (2023) · published 5 July 2023 | Toggle abstract · pdf

  GeV-scale dark matter particles with strong coupling to baryons evade the standard direct detection limits as they are efficiently stopped in the overburden and, consequently, are not able to reach the underground detectors. On the other hand, it has been shown that it is possible to probe this parameter space taking into account the flux of dark matter particles boosted by interactions with cosmic rays. We revisit these bounds paying particular attention to interactions of the relativistic dark matter particles in the Earth's crust. The effects of nuclear form factors, inelastic scattering and extra dependence of the cross section on transferred momentum (e.g. due to presence of light mediators) are studied and are found to be crucial for answering the question as to whether the window for GeV-scale strongly interacting dark matter is closed or not.

  1 citation