Publications

Order by: publication date number of citations

• Large second-order Josephson effect in planar superconductor-semiconductor junctions

  P. Zhang, A. Zarassi, L. Jarjat, V. Van de Sande, M. Pendharkar, J. S. Lee, C. P. Dempsey, A. P. McFadden, S. D. Harrington, J. T. Dong, H. Wu, A. -H. Chen, M. Hocevar, C. J. Palmstrøm, S. M. Frolov

  SciPost Phys. 16, 030 (2024) · published 25 January 2024 | Toggle abstract · pdf

  We investigate the current-phase relations of Al/InAs-quantum well planar Josephson junctions fabricated using nanowire shadowing technique. Based on several experiments, we conclude that the junctions exhibit an unusually large second-order Josephson harmonic, the $\sin(2\varphi)$ term. First, superconducting quantum interference devices (dc-SQUIDs) show half-periodic oscillations, tunable by gate voltages as well as magnetic flux. Second, Josephson junction devices exhibit kinks near half-flux quantum in supercurrent diffraction patterns. Third, half-integer Shapiro steps are present in the junctions. Similar phenomena are observed in Sn/InAs quantum well devices. We perform data fitting to a numerical model with a two-component current phase relation. Analysis including a loop inductance suggests that the sign of the second harmonic term is negative. The microscopic origins of the observed effect remain to be understood. We consider alternative explanations which can account for some but not all of the evidence.

• Measuring the light meson nuclear modification factor in p-Pb collisions over an unprecedented $p_{\text{T}}$ range with ALICE

  Joshua König

  SciPost Phys. Proc. 8, 048 (2022) · published 12 July 2022 | Toggle abstract · pdf

  Differential invariant cross sections of light neutral mesons in p-Pb collisions at $\sqrt{s_{\text{NN}}}$ = 8.16 TeV and in pp collisions at $\sqrt{s}$ = 8 TeV have been measured up to very high transverse momentum ($p_{\text{T}}$). By combining independent reconstruction techniques available in ALICE using the EMCal and PHOS calorimeters as well as the central barrel tracking detectors, the combined spectra cover almost two orders of magnitude in $p_{\rm T}$ for the $\pi^{0}$ meson. The nuclear modification factor $R_{\text{pPb}}$ has been measured for the $\pi^{0}$ and $\eta$ mesons and is found to be consistent with NLO pQCD, CGC and energy loss calculations. Comparisons to the $R_{\text{pPb}}$ of $\pi^{0}$ measured in $\sqrt{s_{\text{NN}}}$ = 5.02 TeV hint at a stronger suppression at low $p_{\rm T}$ with increasing collision energy.

• Transversity through Dihadron: a constrained fit

  Aurore Courtoy

  SciPost Phys. Proc. 8, 049 (2022) · published 12 July 2022 | Toggle abstract · pdf

  We present a study of the valence transversity PDF obtained through a constrained fit. The effects of the constraints on the uncertainties of the PDF are explored. We show that the resulting isovector tensor charge is largely undetermined and, hence, compatible with all lattice evaluations.

• A linear algebra-based approach to understanding the relation between the winding number and zero-energy edge states

  Chen-Shen Lee

  SciPost Phys. Core 7, 003 (2024) · published 30 January 2024 | Toggle abstract · pdf

  The one-to-one relation between the winding number and the number of robust zero-energy edge states, known as bulk-boundary correspondence, is a celebrated feature of 1$d$ systems with chiral symmetry. Although this property can be explained by the K-theory, the underlying mechanism remains elusive. Here, we demonstrate that, even without resorting to advanced mathematical techniques, one can prove this correspondence and clearly illustrate the mechanism using only Cauchy's integral and elementary algebra. Furthermore, our approach to proving bulk-boundary correspondence also provides clear insights into a kind of system that doesn't respect chiral symmetry but can have robust left or right zero-energy edge states. In such systems, one can still assign the winding number to characterize these zero-energy edge states.

• Response functions and cross sections for inclusive neutrino scattering off $^2$H, $^3$H and $^3$He

  Alessandro Grassi, Jacek Golak, Roman Skibiński, Kacper Topolnicki, Henryk Witała, Hiroyuki Kamada, Laura Elisa Marcucci

  SciPost Phys. Proc. 3, 031 (2020) · published 26 February 2020 | Toggle abstract · pdf

  For several decades there has been an interest in studying neutrino scattering on light nuclei, with the hope of increasing knowledge about the theory of weak interactions and electroweak unification. A study of several neutrino induced reactions on light nuclei ($^2$H, $^3$H and $^3$He) is presented here. The cross section for these reactions is evaluated using the nuclear response functions, which holds the information about the nuclear interactions and structure. This approach has been tested for break-up reactions on the deuteron before and is now extended to three-nucleon break-up reactions.

• Tunnelling to holographic traversable wormholes

  Suzanne Bintanja, Ben Freivogel, Andrew Rolph

  SciPost Phys. 16, 066 (2024) · published 5 March 2024 | Toggle abstract · pdf

  We study nonperturbative effects of quantum gravity in a system consisting of a coupled pair of holographic CFTs. The AdS$_4$/CFT$_3$ system has three possible ground states: two copies of empty AdS, a pair of extremal AdS black holes, and an eternal AdS traversable wormhole. We give a recipe for calculating transition rates via gravitational instantons and test it by calculating the emission rate of radiation shells from a black hole. We calculate the nucleation rate of a traversable wormhole between a pair of AdS-RN black holes in the canonical and microcanonical ensembles. Our results give predictions of nonpertubative quantum gravity that can be tested in a holographic simulation.

• Roy Glauber and asymptotic diffraction theory

  Per Osland

  SciPost Phys. Proc. 3, 016 (2020) · published 25 February 2020 | Toggle abstract · pdf

  This is a review of Glauber's asymptotic diffraction theory, in which diffractive scattering is described in terms of interference between semiclassical amplitudes, resulting from a stationary-phase approximation. Typically two such amplitudes are sufficient to accurately describe elastic scattering, but the stationary points are located at complex values of the impact parameter. Their separation controls the interference pattern, and their offsets from the real axis determine the overall fall-off with momentum transfer. Asymptotically, at large momentum transfers, the stationary points move towards singularities of the profile function. I also include some reminiscences from our collaboration.

• Alibis of Exclusion: The role of ethnic economies in the differentiated inclusion of refugees in Berlin

  Jagat Sohail

  Mig. Pol. 2, 002 (2023) · published 11 July 2023 | Toggle abstract · pdf

  Neoliberal transformations in the field of asylum in Germany have, since 2016, placed an emphasis on labour market participation as the primary way through which refugees can establish long-term residence claims. Yet, while new arrivals are increasingly expected to rapidly integrate into this market, they are often armed with differential and precarious legal statuses which overwhelmingly determine the spheres of economic activity refugees can enter. This is especially true for the ever increasing number of rejected asylum seekers who are temporarily “tolerated”, for whom the only path to residence requires that they display their value as economic subjects to the German state. Based on ethnographic fieldwork conducted in Berlin between 2017 and 2020, I argue that, armed with little other than their cultural identities and networks, many refugees heavily relied on co-ethnic relationships to facilitate their participation in the labour market. The result is a displacement of the management of new diversity to ethnic economies, a move that disavows the marginalising consequences of the neoliberal transformations refugees are subject to. By masking a relationship between recently arrived migrants and the German economy and society as a relationship between migrants themselves, I argue that these practices work as alibis of exclusion.

• Derivation of relativistic Yakubovsky equations under Poincaré invariance

  Hiroyuki Kamada

  SciPost Phys. Proc. 3, 003 (2020) · published 24 February 2020 | Toggle abstract · pdf

  Relativistic Faddeev-Yakubovsky four-nucleon scattering equations are derived including a 3-body force. We present these equations in the momentum space representation. The quadratic integral equations using the iteration method, in order to obtain boosted potentials and 3-body force, are demonstrated.

• Soliton confinement in the double sine-Gordon model

  Sergei Rutkevich

  SciPost Phys. 16, 042 (2024) · published 7 February 2024 | Toggle abstract · pdf

  The double sine-Gordon field theory in the weak confinement regime is studied. It represents the small non-integrable deformation of the standard sine-Gordon model caused by the cosine perturbation with the frequency reduced by the factor of 2. This perturbation leads to the confinement of the sine-Gordon solitons, which become coupled into the 'meson' bound states. We classify the meson states in the weak confinement regime, and obtain three asymptotic expansions for their masses, which can be used in different regions of the model parameters. It is shown, that the sine-Gordon breathers, slightly deformed by the perturbation term, transform into the mesons upon increase of the sine-Gordon coupling constant.