Publications

Order by: publication date number of citations

• The quantum cartpole: A benchmark environment for non-linear reinforcement learning

  Kai Meinerz, Simon Trebst, Mark Rudner, Evert van Nieuwenburg

  SciPost Phys. Core 7, 026 (2024) · published 7 May 2024 | Toggle abstract · pdf

  Feedback-based control is the de-facto standard when it comes to controlling classical stochastic systems and processes. However, standard feedback-based control methods are challenged by quantum systems due to measurement induced backaction and partial observability. Here we remedy this by using weak quantum measurements and model-free reinforcement learning agents to perform quantum control. By comparing control algorithms with and without state estimators to stabilize a quantum particle in an unstable state near a local potential energy maximum, we show how a trade-off between state estimation and controllability arises. For the scenario where the classical analogue is highly nonlinear, the reinforcement learned controller has an advantage over the standard controller. Additionally, we demonstrate the feasibility of using transfer learning to develop a quantum control agent trained via reinforcement learning on a classical surrogate of the quantum control problem. Finally, we present results showing how the reinforcement learning control strategy differs from the classical controller in the non-linear scenarios.

• Towards better discrimination and improved modelling of dark-sector showers

  Andy Buckley, Deepak Kar, Sukanya Sinha

  SciPost Phys. Proc. 15, 006 (2024) · published 2 April 2024 | Toggle abstract · pdf

  As no evidence for classic WIMP-based signatures of dark matter have been found at the LHC, several phenomenological studies have raised the possibility of accessing a strongly-interacting dark sector through new collider-event topologies. If dark mesons exist, their evolution and hadronization procedure are currently little constrained. They could decay promptly and result in QCD-like jet structures, even though the original decaying particles are dark sector ones; they could behave as semi-visible jets; or they could behave as completely detector-stable hadrons, in which case the final state is just the missing transverse momentum. In this contribution we will introduce a study performed to explore use of jet substructure methods to distinguish dark-sector from QCD jets in the first two scenarios, using observables in a IRC-safe linear basis, and discuss ways forward for this approach to dark-matter at the LHC.

• Logarithmic corrections for jet production at the LHC

  Emmet P. Byrne

  SciPost Phys. Proc. 10, 010 (2022) · published 10 August 2022 | Toggle abstract · pdf

  Several important processes and analyses at the LHC are sensitive to higher-order perturbative corrections beyond what can currently be calculated at fixed order. One important class of logarithmic corrections are those which appear when the centre-of-mass energy of a QCD collision is much larger than the transverse momenta of the observed jets. We describe the High Energy Jets (HEJ) framework, which includes the dominant high-energy logarithms to provide all-order predictions for several LHC processes including Higgs, $W$, or $Z$ boson production in association with jets. We will summarise some recent developments, in particular the first matching of HEJ to a NLO calculation.

• The origin and evolution of wide Jupiter mass binary objects in young stellar clusters

  Simon Portegies Zwart, Erwan Hochart

  SciPost Astro. 3, 001 (2024) · published 2 July 2024 | Toggle abstract · pdf

  The recently observed population of 540 free-floating Jupiter-mass objects, including 40 dynamically soft pairs, and two triples, in the Trapezium cluster have raised interesting questions on their formation and evolution. We test various scenarios for the origin and survivability of these free floating Jupiter-mass objects and Jupiter-mass Binary Objects (JuMBOs) in the Trapezium cluster. The numerical calculations are performed by direct $N$-body integration of the stars and planets in the Trapezium cluster starting with a wide variety of planets in various configurations. We discuss four models: $\mathcal{SPP}$, in which selected stars have two outer orbiting Jupiter-mass planets; $\mathcal{SPM}$, where selected stars are orbited by Jupiter-mass planet-moon pairs; $\mathcal{ISF}$ in which JuMBOs form in situ with the stars, and $\mathcal{FFC}$, where we introduce a population of free-floating single Jupiter-mass objects, but no initialised binaries. Models $\mathcal{FFC}$ and $\mathcal{SPP}$ fail to produce enough JuMBOs. Models $\mathcal{SPM}$ can produce sufficient free-floaters and JuMBOs, but requires unusually wide orbits for the planet-moon system around the star. The observed JuMBOs and free-floating Jupiter-mass objects in the Trapezium cluster are best reproduced if they formed in pairs and as free-floaters together with the other stars in a smooth (Plummer) density profile with a virial radius of $\sim 0.5$pc. A fractal (with fractal dimension 1.6) stellar density distribution also works, but requires relatively recent formations ($\raise-.5ex\hbox{$\buildrel>\over\sim$} 0.2$Myr after the other stars formed) or a high ($\raise-.5ex\hbox{$\buildrel>\over\sim$} 50$%) initial binary fraction. This would make the primordial binary fraction of JuMBOs even higher than the already large observation fraction of $\sim 8$% (42/540). The fraction of JuMBOs will continue to drop with time, and the lack of JuMBOs in Upper Scorpius could then result in its higher age, causing more JuMBOs to be ionized. We then also predict that the interstellar density of Jupiter-mass objects (mostly singles with some $\sim 2$% lucky surviving binaries) is $\sim 0.05$ per pc$^{-3}$ (or around 0.24 per star).

• Dark matter or millisecond pulsars? A deep learning-based analysis of the Fermi Galactic Centre Excess

  Florian List, Nicholas L. Rodd, Geraint F. Lewis

  SciPost Phys. Proc. 12, 034 (2023) · published 4 July 2023 | Toggle abstract · pdf

  The $\gamma$-ray Galactic Centre Excess (GCE) remains one of the few observed high-energy signals for which a dark matter (DM) origin is a plausible explanation. We present a deep learning-based analysis of the $\gamma$-ray sky in the Galactic Centre region, carefully accounting for the mathematical degeneracy between faint point-sources (PSs) such as millisecond pulsars (MSPs) and DM-like Poisson emission. Using recent models for the Galactic foregrounds, we find that relatively few bright PSs just below Fermi's detection threshold seem unlikely to explain the GCE, although we continue to find evidence for PSs. Looking ahead, further improvements in the modelling of the $\gamma$-ray sky will be crucial for distinguishing between a DM-like and point-like morphology of the signal.

• Hadron Production in terms of Green's Functions in Non-Equilibrium Matter

  A. V. Koshelkin

  SciPost Phys. Proc. 10, 037 (2022) · published 11 August 2022 | Toggle abstract · pdf

  Following the quark-hadron duality concept, we show that the number of hadrons generated in the deconfinement matter is entirely determined by the exact non-equilibrium Green's functions of partons in the medium and the vertex function governing the probability of the confinement-deconfinement phase transition. In such an approach, compactifying the standard (3+1) chromodynamics into $ QCD_{xy} + QCD_{zt}$, the rate of the hadrons produced in particle collisions is derived in the explicit form provided that the hadronization is the first order phase transition. The pion production is found to be in good agreement to the experimental results on the pion yield in pp collisions.

• Comments on the negative grade KdV hierarchy

  Y. F. Adans, Jose F. Gomes, G. V. Lobo, A. H. Zimerman

  SciPost Phys. Proc. 14, 014 (2023) · published 23 November 2023 | Toggle abstract · pdf

  The construction of negative grade KdV hierarchy is proposed in terms of a Miura-gauge transformation. Such gauge transformation is employed within the zero curvature representation and maps the Lax operator of the mKdV into its couterpart within the KdV setting. Each odd negative KdV flow is obtained from an odd and its subsequent even negative mKdV flows. The negative KdV flows are shown to inherit the two different vacua structure that characterizes the associated mKdV flows.

• Efficient adaptive Bayesian estimation of a slowly fluctuating Overhauser field gradient

  Jacob Benestad, Jan A. Krzywda, Evert van Nieuwenburg, Jeroen Danon

  SciPost Phys. 17, 014 (2024) · published 16 July 2024 | Toggle abstract · pdf

  Slow fluctuations of Overhauser fields are an important source for decoherence in spin qubits hosted in III-V semiconductor quantum dots. Focusing on the effect of the field gradient on double-dot singlet-triplet qubits, we present two adaptive Bayesian schemes to estimate the magnitude of the gradient by a series of free induction decay experiments. We concentrate on reducing the computational overhead, with a real-time implementation of the schemes in mind. We show how it is possible to achieve a significant improvement of estimation accuracy compared to more traditional estimation methods. We include an analysis of the effects of dephasing and the drift of the gradient itself.

• Geometric surprises in the Python's lunch conjecture

  Gurbir Arora, Matthew Headrick, Albion Lawrence, Martin Sasieta, Connor Wolfe

  SciPost Phys. 16, 152 (2024) · published 12 June 2024 | Toggle abstract · pdf

  A bulge surface, on a time reflection-symmetric Cauchy slice of a holographic spacetime, is a non-minimal extremal surface that occurs between two locally minimal surfaces homologous to a given boundary region. According to the python's lunch conjecture of Brown et al., the bulge's area controls the complexity of bulk reconstruction, in the sense of the amount of post-selection that needs to be overcome for the reconstruction of the entanglement wedge beyond the outermost extremal surface. We study the geometry of bulges in a variety of classical spacetimes, and discover a number of surprising features that distinguish them from more familiar extremal surfaces such as Ryu-Takayanagi surfaces: they spontaneously break spatial isometries, both continuous and discrete; they are sensitive to the choice of boundary infrared regulator; they can self-intersect; and they probe entanglement shadows, orbifold singularities, and compact spaces such as the sphere in AdS$_p× S^q$. These features imply, according to the python's lunch conjecture, novel qualitative differences between complexity and entanglement in the holographic context. We also find, surprisingly, that extended black brane interiors have a non-extensive complexity; similarly, for multi-boundary wormhole states, the complexity pleateaus after a certain number of boundaries have been included.

• Tchavdar Dimitrov Palev - In memoriam

  N. I. Stoilova

  SciPost Phys. Proc. 14, 011 (2023) · published 23 November 2023 | Toggle abstract · pdf

  Tchavdar Dimitrov Palev – In memoriam