Publications

Order by: publication date number of citations

• Equal-time approach to real-time dynamics of quantum fields

  Robert Ott, Torsten V. Zache, Jürgen Berges

  SciPost Phys. 14, 011 (2023) · published 1 February 2023 | Toggle abstract · pdf

  We employ the equal-time formulation of quantum field theory to derive effective kinetic theories, first for a weakly coupled non-relativistic Bose gas, and then for a strongly correlated system of self-interacting $N$-component fields. Our results provide the link between state-of-the-art measurements of equal-time effective actions using quantum simulator platforms, as employed in [Phys. Rev. X 10, 011020 (2020); Nat. Phys. 16, 1012 (2020)], and observables underlying effective kinetic or hydrodynamic descriptions. New non-perturbative approximation schemes can be developed and certified this way, where the a priori time-local formulation of the equal-time effective action has crucial advantages over the conventional closed-time-path approach which is non-local in time.

  1 citation

• An overview of lattice results for parton distribution functions

  Luigi Del Debbio

  SciPost Phys. Proc. 15, 028 (2024) · published 3 April 2024 | Toggle abstract · pdf

  Following a ground-breaking proposal by Ji [Phys. Rev. Lett. 110, 262002 (2013)], numerical simulations of Quantum Chromo Dynamics (QCD) on a Euclidean lattice have provided new, valuable information on the structure of hadrons. In this talk, we briefly review the lattice approach to the reconstruction of parton densities, highlighting the connection between lattice observables and parton densities, with a focus on theoretical issues. Since parton distributions are extracted from lattice data by solving an inverse problem, we discuss some of the difficulties that affect these determinations and how they can be formulated in a Bayesian framework.

  1 citation

• Hole doping and electronic correlations in Cr substituted BaFe$_{2}$As$_{2}$

  Marli dos Reis Cantarino, Kevin R. Pakuszewski, Bjoern Salzmann, Pedro H. A. Moya, Wagner R. da Silva Neto, Gabriel S. Freitas, Pascoal G. Pagliuso, Cris Adriano, Walber H. Brito, Fernando A. Garcia

  SciPost Phys. 17, 141 (2024) · published 22 November 2024 | Toggle abstract · pdf

  For a significant composition range, the suppression of the spin density wave transition temperature ($T_{\text{SDW}}$) in Cr- and Mn-substituted BaFe$_{2}$As$_{2}$ (CrBFA and MnBFA, respectively) coincides as a function of Cr/Mn content, despite the distinct electronic effects of these substitutions. Additionally, for any Cr/Mn content superconductivity (SC) is absent and this topic is particularly less explored in the case of CrBFA. In this work, we employ angle-resolved photoemission spectroscopy (ARPES) and combined density functional theory plus dynamical mean field theory (DFT+DMFT) to address the evolution of the Fermi surface (FS) and electronic correlations in CrBFA. Our findings reveal that incorporating Cr leads to an effective hole doping of the states near the FS, which is well described within the virtual crystal approximation (VCA). Moreover, analysis of the ARPES spectra of the bands with main $d_{yz}$-orbital character reveals a fractional scaling of the imaginary part of self-energy as a function of the binding energy, a signature property of Hund's correlations. Our DFT+DMFT calculations support these experimental findings. We conclude that CrBFA is a correlated electron system for which the changes in the FS as a function of Cr are unrelated to the suppression of $T_{\text{SDW}}$. In addition, we suggest that the absence of SC is primarily due to the competition between Cr local moments and the Fe-derived itinerant spin fluctuations.

  1 citation

• How to determine the shape of nuclear molecules with polarized gamma-rays

  Lorenzo Fortunato

  SciPost Phys. Proc. 3, 035 (2020) · published 26 February 2020 | Toggle abstract · pdf

  A method has been recently proposed to establish the geometry of the alpha-cluster arrangement in $^{12}$C making use of polarized gamma-rays. The ratio of intensities of scattered radiation at 90 degrees along and perpendicular to the initial direction of the electric field vector, called depolarization ratio, is a key quantity that allows to underpin the nature of totally symmetric modes of vibrations. This allows to connect with the underlying point-group structure and therefore to the geometric shape of the nuclear molecule. This method is reviewed for $^{12}$C and extended to other configurations, such as three unequal clusters and four identical clusters (e.g. $^{16}$O).

  1 citation

• A proposal to extract and enhance four-Majorana interactions in hybrid nanowires

  Tasnum Reza, Sergey M. Frolov, David Pekker

  SciPost Phys. 13, 120 (2022) · published 7 December 2022 | Toggle abstract · pdf

  We simulate the smallest building block of the Sachdev-Ye-Kitaev (SYK) model, a system of four interacting Majorana modes. We propose a 1D Kitaev chain that has been split into three segments, i.e., two topological segments separated by a non-topological segment in the middle, hosting four Majorana Zero Modes at the ends of the topological segments. We add a non-local interaction term to this Hamiltonian which produces both bilinear (two-body) interactions and a quartic (four-body) interaction between the Majorana modes. We further tune the parameters in the Hamiltonian to reach the regime with a finite quartic interaction strength and close to zero bilinear interaction strength, as required by the SYK model. To achieve this, we map the Hamiltonian from Majorana basis to a complex fermion basis, and extract the interaction strengths using a method of characterization of low-lying energy levels and then finding the differences in energies between odd and even parity levels. We show that the interaction strengths can be tuned using two methods - (i) an approximate method of tuning overlapping Majorana wave functions (without non-local interactions) to a zero energy point followed by addition of a non-local interaction, and (ii) a direct parameter space optimization method using a genetic algorithm. We propose that this model could be further extended to more Majorana modes, and show a 6-Majorana model as an example. Since eigenspectral characterization of one-dimensional nanowire devices can be done via tunneling spectroscopy in quantum transport measurements, this study could be performed in experiment.

  1 citation

• The Tunka-Grande scintillation array: Current results

  A. L. Ivanova, I. Astapov, P. Bezyazeekov, E. Bonvech, A. Borodin, N. Budnev, A. Bulan, D. Chernov, A. Chiavassa, A. Dyachok, A. Gafarov, A. Garmash, V. Grebenyuk, E. Gress, O. Gress, T. Gress, A. Grinyuk, O. Grishin, A. D. Ivanova, N. Kalmykov, V. Kindin, S. Kiryuhin, R. Kokoulin, K. Kompaniets, E. Korosteleva, V. Kozhin, E. Kravchenko, A. Kryukov, L. Kuzmichev, A. Lagutin, M. Lavrova, Y. Lemeshev, B. Lubsandorzhiev, N. Lubsandorzhiev, A. Lukanov, D. Lukyantsev, S. Malakhov, R. Mirgazov, R. Monkhoev, E. Osipova, A. Pakhorukov, L. Pankov, A. Pan, A. Panov, A. Petrukhin, I. Poddubnyi, D. Podgrudkov, V. Poleschuk, V. Ponomareva, E. Popova, E. Postnikov, V. Prosin, V. Ptuskin, A. Pushnin, R. Raikin, A. Razumov, G. Rubtsov, E. Ryabov, Y. Sagan, V. Samoliga, A. Satyshev, A. Silaev, A. Silaev, A. Sidorenkov, A. Skurikhin, A. Sokolov, L. Sveshnikova, V. Tabolenko, L. Tkachev, A. Tanaev, M. Ternovoy, R. Togoo, N. Ushakov, A. Vaidyanathan, P. Volchugov, N. Volkov, D. Voronin, A. Zagorodnikov, D. Zhurov, I. Yashin

  SciPost Phys. Proc. 13, 011 (2023) · published 28 September 2023 | Toggle abstract · pdf

  The Tunka-Grande experiment is a scintillation array with about 0.5 km$^2$ sensitive area at Tunka Valley, Siberia, for measuring charged particles and muons in extensive air showers (EASs). Tunka-Grande is optimized for cosmic ray studies in the energy range 10 PeV to about 1 EeV, where exploring the composition is of fundamental importance for understanding the transition from galactic to extragalactic origin of cosmic rays. This paper attempts to provide a synopsis of the current results of the experiment. In particular, the reconstruction of the all-particle energy spectrum in the range of 10 PeV to 1 EeV based on experimental data from four observation seasons is presented.

  1 citation

• Recent results from the TOTEM collaboration and the discovery of the odderon

  Christophe Royon

  SciPost Phys. Proc. 13, 005 (2023) · published 28 September 2023 | Toggle abstract · pdf

  We describe the most recent results from the TOTEM collaboration on elastic, inelastic and total cross sections as well as the odderon discovery by the D0 and TOTEM collaborations.

  1 citation

• Cosmic ray measurements with IceCube and IceTop

  Dennis Soldin (for the IceCube Collaboration)

  SciPost Phys. Proc. 13, 002 (2023) · published 28 September 2023 | Toggle abstract · pdf

  IceCube is a cubic-kilometer Cherenkov detector in the deep ice at the geographic South Pole. The dominant event yield in the deep ice detector consists of penetrating atmospheric muons with energies above approximately 300 GeV, produced in cosmic ray air showers. In addition, the surface array, IceTop, measures the electromagnetic component and GeV muons of air showers. Hence, IceCube and IceTop yield unique opportunities to study cosmic rays with unprecedented statistics in great detail. We will present recent results of comic ray measurements from IceCube and IceTop. In this overview, we will highlight measurements of the energy spectrum of cosmic rays from 250 TeV up to the EeV range and their mass composition above 3 PeV. We will also report recent results from measurements of the muon content in air showers and discuss their consistency with predictions from current hadronic interaction models.

  1 citation

• Amplitude and colour evolution

  Simon Plätzer

  SciPost Phys. Proc. 15, 007 (2024) · published 2 April 2024 | Toggle abstract · pdf

  Colour evolution and parton branching at the amplitude level have become important theoretical frameworks to improve parton showers, and are algorithms in their own right: They complement shower development by resummation algorithms capable of including interference effects and subleading colour contributions at an unprecedented level. I summarize recent development in the field, focusing on soft gluon evolution, hadronization, and the CVolver framework.

  1 citation

• Measurement of 3He analyzing power for p-3He scattering using the polarized 3He target

  A. Watanabe, S. Nakai, K. Sekiguchi, T. Akieda, D. Etoh, M. Inoue, Y. Inoue, K. Kawahara, H. Kon, K. Miki, T. Mukai, D. Sakai, S. Shibuya, Y. Shiokawa, T. Taguchi, H. Umetsu, Y. Utsuki, Y. Wada, M. Watanabe, M. Itoh, T. Ino, T. Wakui, K. Hatanaka, H. Kanda, H. J. Ong, D. T. Tran, S. Goto, Y. Hirai, D. Inomoto, H. Kasahara, S. Mitsumoto, H. Oshiro, T. Wakasa, Y. Maeda, K. Nonaka, H. Sakai, T. Uesaka

  SciPost Phys. Proc. 3, 020 (2020) · published 25 February 2020 | Toggle abstract · pdf

  Proton–3He scattering is one of the good probes to study the T = 3/2 channel of three– nucleon forces. We have measured 3He analyzing powers for p−3He elastic scattering with the polarized 3He target at 70 and 100 MeV. In the conference the data were com- pared with the theoretical predictions based on the modern nucleon–nucleon potentials. Large discrepancies were found between the data and the calculations at the angles where the 3He analyzing power takes the minimum and maximum values.

  1 citation