Showing papers by "International School for Advanced Studies published in 2022"
TL;DR: In this paper , the problem of automatically detecting the correct pre-processing transformation in a statistical learning framework by implementing a deep-learning architecture is addressed, which can generalise the existing approaches of linear subspace manipulation to non-linear hyperbolic problems with unknown advection fields.
16 citations
TL;DR: In this article , the authors apply the form factor bootstrap approach to branch point twist fields in the q-state Potts model for q ≤ 3 and present form factor solutions both for the standard branch point-twill field with q ≥ 3 and for the composite (or symmetry resolved) branch-point twist field with Q ≥ 3.
Abstract: A bstract In this paper, we apply the form factor bootstrap approach to branch point twist fields in the q -state Potts model for q ≤ 3. For q = 3 this is an integrable interacting quantum field theory with an internal discrete ℤ 3 symmetry and therefore provides an ideal starting point for the investigation of the symmetry resolved entanglement entropies. However, more generally, for q ≤ 3 the standard Rényi and entanglement entropies are also accessible through the bootstrap programme. In our work we present form factor solutions both for the standard branch point twist field with q ≤ 3 and for the composite (or symmetry resolved) branch point twist field with q = 3. In both cases, the form factor equations are solved for two particles and the solutions are carefully checked via the ∆-sum rule. Using our analytic predictions, we compute the leading finite-size corrections to the entanglement entropy and entanglement equipartition for a single interval in the ground state.
13 citations
TL;DR: In this paper , the authors investigated the cross-correlation between resolved gravitational wave detections and the neutral hydrogen (HI) signal from intensity mapping (IM) experiments, and showed that the GW redshift distribution can be calibrated with good accuracy at low redshifts, without any assumptions on cosmology or astrophysics.
Abstract: Two of the most rapidly growing observables in cosmology and astrophysics are gravitational waves (GW) and the neutral hydrogen (HI) distribution. In this work, we investigate the cross-correlation between resolved gravitational wave detections and HI signal from intensity mapping (IM) experiments. By using a tomographic approach with angular power spectra, including all projection effects, we explore possible applications of the combination of the Einstein Telescope and the SKAO intensity mapping surveys. We focus on three main topics: \textit{(i)} statistical inference of the observed redshift distribution of GWs; \textit{(ii)} constraints on dynamical dark energy models as an example of cosmological studies; \textit{(iii)} determination of the nature of the progenitors of merging binary black holes, distinguishing between primordial and astrophysical origin. Our results show that: \textit{(i)} the GW redshift distribution can be calibrated with good accuracy at low redshifts, without any assumptions on cosmology or astrophysics, potentially providing a way to probe astrophysical and cosmological models; \textit{(ii)} the constrains on the dynamical dark energy parameters are competitive with IM-only experiments, in a complementary way and potentially with less systematics; \textit{(iii)} it will be possible to detect a relatively small abundance of primordial black holes within the gravitational waves from resolved mergers. Our results extend towards $\mathrm{GW \times IM}$ the promising field of multi-tracing cosmology and astrophysics, which has the major advantage of allowing scientific investigations in ways that would not be possible by looking at single observables separately.
8 citations
TL;DR: In this paper , the entanglement content of integrable spin-1/2 XXX and XXZ chains in the scaling limit was analyzed and the number of excited magnons with respect to the size of the system is small.
Abstract: We calculate exactly the entanglement content of magnon excited states in the integrable spin-1/2 XXX and XXZ chains in the scaling limit. In particular, we show that as far as the number of excited magnons with respect to the size of the system is small one can decompose the entanglement content, in the scaling limit, to the sum of the entanglement of particular excited states of free fermionic or bosonic theories. In addition we conjecture that the entanglement content of the generic translational invariant free fermionic and bosonic Hamiltonians can be also classified, in the scaling limit, with respect to the entanglement content of the fermionic and bosonic chains with the number operator as the Hamiltonian in certain circumstances. Our results effectively classify the entanglement content of wide range of integrable spin chains in the scaling limit.
6 citations
TL;DR: In this paper , the authors proposed a reduced order method to solve a parametrized optimal control problem governed by shallow waters equations in a solution tracking setting, where the objective is to reproduce the desired velocity and height profiles faster than the standard model.
Abstract: Abstract In the present paper we propose reduced order methods as a reliable strategy to efficiently solve parametrized optimal control problems governed by shallow waters equations in a solution tracking setting. The physical parametrized model we deal with is nonlinear and time dependent: this leads to very time consuming simulations which can be unbearable, e.g., in a marine environmental monitoring plan application. Our aim is to show how reduced order modelling could help in studying different configurations and phenomena in a fast way. After building the optimality system, we rely on a POD-Galerkin reduction in order to solve the optimal control problem in a low dimensional reduced space. The presented theoretical framework is actually suited to general nonlinear time dependent optimal control problems. The proposed methodology is finally tested with a numerical experiment: the reduced optimal control problem governed by shallow waters equations reproduces the desired velocity and height profiles faster than the standard model, still remaining accurate.
6 citations
TL;DR: In this paper , the authors show that the results of the EHT collaboration hold only for unnaturally small values of the absorption coefficient (i.e. much lower than 10 -14 ), and thus have to be significantly revised in scenarios with physical significance.
Abstract: Abstract The images of Sagittarius A* recently released by the Event Horizon Telescope collaboration have been accompanied [ Astrophys. J. Lett. 930 (2022) L17] by an analysis of the constraints on the possible absence of a trapping horizon, i.e. on the possibility that the object at the center of our galaxy is an ultra-compact object with a surface re-emitting incident radiation. Using the observed image size and the broadband spectrum of Sgr A*, it is claimed that the radius of any surface, in which incident radiation is re-emitted thermally, is strongly bounded from above by these latest observations. Herein, we discuss how the reported constraint relies on the extremely strong assumption of perfect balance in the energy exchange between the accretion disk and the central object, and show that this is violated whenever the surface is endowed with any non-zero absorption coefficient. We derive the upper-bound constraints that can be cast on the radius and dimensionless absorption coefficient of the surface. We show that the conclusions of the analysis presented by the EHT collaboration hold only for unnaturally small values of the absorption coefficient (i.e. much lower than 10 -14 ), and thus have to be significantly revised in scenarios with physical significance.
6 citations
TL;DR: In this article , the role of numerical stabilization in reduced order models (ROMs) of marginally-resolved, convection-dominated incompressible flows is investigated, that is, whether the numerical stabilization is beneficial both at the FOM and the ROM level.
Abstract: Numerical stabilization is often used to eliminate (alleviate) the spurious oscillations generally produced by full order models (FOMs) in under-resolved or marginally-resolved simulations of convection-dominated flows. In this article, we investigate the role of numerical stabilization in reduced order models (ROMs) of marginally-resolved, convection-dominated incompressible flows. Specifically, we investigate the FOM–ROM consistency, that is, whether the numerical stabilization is beneficial both at the FOM and the ROM level. As a numerical stabilization strategy, we focus on the evolve-filter-relax (EFR) regularization algorithm, which centers around spatial filtering. To investigate the FOM-ROM consistency, we consider two ROM strategies: (i) the EFR-noEFR, in which the EFR stabilization is used at the FOM level, but not at the ROM level; and (ii) the EFR-EFR, in which the EFR stabilization is used both at the FOM and at the ROM level. We compare the EFR-noEFR with the EFR-EFR in the numerical simulation of a 2D incompressible flow past a circular cylinder in the convection-dominated, marginally-resolved regime. We also perform model reduction with respect to both time and Reynolds number. Our numerical investigation shows that the EFR-EFR is more accurate than the EFR-noEFR, which suggests that FOM-ROM consistency is beneficial in convection-dominated, marginally-resolved flows.
5 citations
TL;DR: In this paper , a joint experimental-theoretical approach uncovers a remarkable out-of-equilibrium phenomenon: photo-induced stabilisation of the long sought monoclinic metal phase, which is absent at equilibrium and in homogeneous materials, but emerges as a metastable state solely when light excitation is combined with the underlying nanotexture.
Abstract: Mott transitions in real materials are first order and almost always associated with lattice distortions, both features promoting the emergence of nanotextured phases. This nanoscale self-organization creates spatially inhomogeneous regions, which can host and protect transient non-thermal electronic and lattice states triggered by light excitation. Here, we combine time-resolved X-ray microscopy with a Landau-Ginzburg functional approach for calculating the strain and electronic real-space configurations. We investigate V2O3, the archetypal Mott insulator in which nanoscale self-organization already exists in the low-temperature monoclinic phase and strongly affects the transition towards the high-temperature corundum metallic phase. Our joint experimental-theoretical approach uncovers a remarkable out-of-equilibrium phenomenon: the photo-induced stabilisation of the long sought monoclinic metal phase, which is absent at equilibrium and in homogeneous materials, but emerges as a metastable state solely when light excitation is combined with the underlying nanotexture of the monoclinic lattice.
5 citations
TL;DR: In this article , a spectral approach to the Benjamin-Feir instability phenomenon using a symplectic version of Kato's theory of similarity transformation to reduce the problem to determine the eigenvalues of a $$ 4 \times 4 $$ was proposed.
Abstract: Abstract Small-amplitude, traveling, space periodic solutions –called Stokes waves– of the 2 dimensional gravity water waves equations in deep water are linearly unstable with respect to long-wave perturbations, as predicted by Benjamin and Feir in 1967. We completely describe the behavior of the four eigenvalues close to zero of the linearized equations at the Stokes wave, as the Floquet exponent is turned on. We prove in particular the conjecture that a pair of non-purely imaginary eigenvalues depicts a closed figure “8”, parameterized by the Floquet exponent, in full agreement with numerical simulations. Our new spectral approach to the Benjamin-Feir instability phenomenon uses a symplectic version of Kato’s theory of similarity transformation to reduce the problem to determine the eigenvalues of a $$ 4 \times 4 $$ 4 × 4 complex Hamiltonian and reversible matrix. Applying a procedure inspired by KAM theory, we block-diagonalize such matrix into a pair of $$2 \times 2 $$ 2 × 2 Hamiltonian and reversible matrices, thus obtaining the full description of its eigenvalues.
5 citations
TL;DR: An intriguing identity in the shuffle algebra is proved, first observed in [CGM19] in the setting of lattice paths, which has a close connection to de Bruijn's formula when interpreted in the framework of signatures of paths.
4 citations
TL;DR: Investigation of healthiness evaluations of males and females shows that different dimensions are associated to healthiness of a food for females and males, and different dimensions could be leveraged to develop sex-targeted interventions depending on the type of food.
TL;DR: In this article, the influence of thermal effects on superlocalization and on heating efficiency was studied theoretically, and it was shown that when time-dependent steady state motions of the magnetisation vector are present in the zero temperature limit, then deterministic and stochastic results are very similar to each other.
TL;DR: For instance, this paper found that adults associate the processed form of a food with safety more than its unprocessed form since processing techniques, which are ubiquitously applied in different cultures, often reduce the toxicity of foods, and signal previous human intervention and intended consumption.
TL;DR: In this paper , the ground state of a theory composed by M species of massless complex bosons in one dimension coupled together via a conformal interface is considered, and both the Rényi entropy and the negativity of a generic partition of wires, generalizing the approach developed in a recent work for free fermions, are computed.
Abstract: A bstract We consider the ground state of a theory composed by M species of massless complex bosons in one dimension coupled together via a conformal interface. We compute both the Rényi entropy and the negativity of a generic partition of wires, generalizing the approach developed in a recent work for free fermions. These entanglement measures show a logarithmic growth with the system size, and the universal prefactor depends both on the details of the interface and the bipartition. We test our analytical predictions against exact numerical results for the harmonic chain.
TL;DR: In this paper, the authors studied Schrodinger operators with Floquet boundary conditions on flat tori and obtained a spectral result giving an asymptotic expansion of all the eigenvalues.
Abstract: We study Schrodinger operators with Floquet boundary conditions on flat tori obtaining a spectral result giving an asymptotic expansion of all the eigenvalues. The expansion is in λ − δ with δ ∈ ( 0 , 1 ) for most of the eigenvalues λ (stable eigenvalues), while it is a “directional expansion” for the remaining eigenvalues (unstable eigenvalues). The proof is based on a structure theorem which is a variant of the one proved in [31] , [32] and on a new iterative quasimode argument.
TL;DR: In this article, the authors summarize the efforts made by us and other groups to rationalize this behavior in terms of the mathematical language and tools of polymer physics and turn these ideas into a multi-scale numerical algorithm which is described here in full details.
Abstract: Fluorescence in situ hybridization and chromosome conformation capture methods point to the same conclusion: that chromosomes appear to the external observer as compact structures with a highly nonrandom three-dimensional organization. In this work, we recapitulate the efforts made by us and other groups to rationalize this behavior in terms of the mathematical language and tools of polymer physics. After a brief introduction dedicated to some crucial experiments dissecting the structure of interphase chromosomes, we discuss at a nonspecialistic level some fundamental aspects of theoretical and numerical polymer physics. Then, we inglobe biological and polymer aspects into a polymer model for interphase chromosomes which moves from the observation that mutual topological constraints, such as those typically present between polymer chains in ordinary melts, induce slow chain dynamics and "constraint" chromosomes to resemble double-folded randomly branched polymer conformations. By explicitly turning these ideas into a multi-scale numerical algorithm which is described here in full details, we can design accurate model polymer conformations for interphase chromosomes and offer them for systematic comparison to experiments. The review is concluded by discussing the limitations of our approach and pointing to promising perspectives for future work.
TL;DR: In this article, a general framework based on symplectic geometry for the study of second order conditions in constrained variational problems on curves is discussed, and Morse-type theorems that connect the negative inertia index of the Hessian of the problem to some symplectic invariants of Jacobi curves are shown.
Abstract: In this paper we discuss a general framework based on symplectic geometry for the study of second order conditions in constrained variational problems on curves. Using the notion of L -derivatives we construct Jacobi curves, which represent a generalisation of Jacobi fields from the classical calculus of variations, but which also works for non-smooth extremals. This construction includes in particular the previously known constructions for specific types of extremals. We state and prove Morse-type theorems that connect the negative inertia index of the Hessian of the problem to some symplectic invariants of Jacobi curves.
TL;DR: In this paper , the effect of a continuous flow LVAD device on the aortic flow is investigated by means of a non-intrusive reduced order model (ROM) built using the proper orthogonal decomposition with interpolation (PODI) method based on radial basis functions (RBF).
TL;DR: In this article , the authors investigated the mechanisms underlying duration perception by looking for a neural signature of subjective time distortion induced by motion adaptation and found that perceived duration can be predicted by the amplitude of the N200 event-related potential evoked by the adapted stimulus.
TL;DR: In this paper , a reduced-order model for Navier-Stokes flow systems is presented, which is based on Proper Orthogonal Decomposition within a level-set geometry description and discretized by the Finite Element Method.
Abstract: We focus on steady and unsteady Navier–Stokes flow systems in a reduced-order modeling framework based on Proper Orthogonal Decomposition within a levelset geometry description and discretized by an unfitted mesh Finite Element Method. This work extends the approaches of [1], [2], [3] to nonlinear CutFEM discretization. We construct and investigate a unified and geometry independent reduced basis which overcomes many barriers and complications of the past, that may occur whenever geometrical morphings are taking place. By employing a geometry independent reduced basis, we are able to avoid remeshing and transformation to reference configurations, and we are able to handle complex geometries. This combination of a fixed background mesh in a fixed extended background geometry with reduced order techniques appears beneficial and advantageous in many industrial and engineering applications, which could not be resolved efficiently in the past.
TL;DR: In this article , the authors study particle collisions near Kerr black holes, by reviewing and extending the so far proposed scenarios, and show that these scenarios involving near-horizon target particles are in principle able to attain, sub-Planckian, but still ultra-high center of mass energies of the order of $10−23−10−25$ eV even for non-extremal Kerr Black Holes.
Abstract: The possibility that rotating black holes could be natural particle accelerators has been subject of intense debate. While it appears that for extremal Kerr black holes arbitrarily high center of mass energies could be achieved, several works pointed out that both theoretical as well as astrophysical arguments would severely dampen the attainable energies. In this work we study particle collisions near Kerr black holes, by reviewing and extending the so far proposed scenarios. Most noticeably, we shall focus on the recently advanced target particle scenarios which were claimed to reach arbitrarily high energies even for Schwarzschild black holes. By implementing the hoop conjecture we show that these scenarios involving near-horizon target particles are in principle able to attain, sub-Planckian, but still ultra-high center of mass energies of the order of $10^{23}-10^{25}$ eV even for non-extremal Kerr black holes. Furthermore, analysing the properties of particles produced in such collisions, we find that photons can escape to infinity. However, their energy is only of the order of the energy of the colliding particles and hence relatively low, which is the same conclusion previously reached in the literature about the original Ba\~nados--Silk--West process. This finding points towards a general limitation of collisional Penrose processes, at least for what concerns their primary products.
TL;DR: In this article , it was shown that by scaling nearest-neighbour ferromagnetic energies defined on Poisson random sets in the plane one obtains an isotropic perimeter energy with a surface tension characterised by an asymptotic formula.
Abstract: We prove that by scaling nearest-neighbour ferromagnetic energies defined on Poisson random sets in the plane one obtains an isotropic perimeter energy with a surface tension characterised by an asymptotic formula. The result relies on proving that cells with ‘very long’ or ‘very short’ edges of the corresponding Voronoi tessellation can be neglected. In this way we may apply Geometry Measure Theory tools to define a compact convergence, and a characterisation of metric properties of clusters of Voronoi cells using limit theorems for subadditive processes.
TL;DR: In this article , the authors proposed a learning model with two main parameters, the rank of the feedback learning matrix and the tolerance to spike timing τ⋆, and demonstrated that a low (high) rank accounts for an error-based (target-based) learning rule, while high (low) tolerance to spikes timing promotes rate-based coding.
Abstract: The field of recurrent neural networks is over-populated by a variety of proposed learning rules and protocols. The scope of this work is to define a generalized framework, to move a step forward towards the unification of this fragmented scenario. In the field of supervised learning, two opposite approaches stand out, error-based and target-based. This duality gave rise to a scientific debate on which learning framework is the most likely to be implemented in biological networks of neurons. Moreover, the existence of spikes raises the question of whether the coding of information is rate-based or spike-based. To face these questions, we proposed a learning model with two main parameters, the rank of the feedback learning matrix [Formula: see text] and the tolerance to spike timing τ⋆. We demonstrate that a low (high) rank [Formula: see text] accounts for an error-based (target-based) learning rule, while high (low) tolerance to spike timing promotes rate-based (spike-based) coding. We show that in a store and recall task, high-ranks allow for lower MSE values, while low-ranks enable a faster convergence. Our framework naturally lends itself to Behavioral Cloning and allows for efficiently solving relevant closed-loop tasks, investigating what parameters [Formula: see text] are optimal to solve a specific task. We found that a high [Formula: see text] is essential for tasks that require retaining memory for a long time (Button and Food). On the other hand, this is not relevant for a motor task (the 2D Bipedal Walker). In this case, we find that precise spike-based coding enables optimal performances. Finally, we show that our theoretical formulation allows for defining protocols to estimate the rank of the feedback error in biological networks. We release a PyTorch implementation of our model supporting GPU parallelization.
TL;DR: In this article , a space-time POD-Galerkin reduction is proposed to solve the optimal control problem in a low dimensional reduced space in a fast way for several parametric instances.
Abstract: In this contribution we propose reduced order methods to fast and reliably solve parametrized optimal control problems governed by time dependent nonlinear partial differential equations. Our goal is to provide a tool to deal with the time evolution of several nonlinear optimality systems in many-query context, where a system must be analyzed for various physical and geometrical features. Optimal control can be used in order to fill the gap between collected data and mathematical model and it is usually related to very time consuming activities: inverse problems, statistics, etc. Standard discretization techniques may lead to unbearable simulations for real applications. We aim at showing how reduced order modeling can solve this issue. We rely on a space-time POD-Galerkin reduction in order to solve the optimal control problem in a low dimensional reduced space in a fast way for several parametric instances. The proposed algorithm is validated with a numerical test based on environmental sciences: a reduced optimal control problem governed by viscous Shallow Waters Equations parametrized not only in the physics features, but also in the geometrical ones. We will show how the reduced model can be useful in order to recover desired velocity and height profiles more rapidly with respect to the standard simulation, not loosing in accuracy.
TL;DR: In this paper , the authors proposed a method for the removal of the constant term of the potential of the quantum anharmonic oscillator in the high energy (UV) limit of the nonperturbative renormalization group.
Abstract: Due to its construction, the nonperturbative renormalization group (RG) evolution of the constant, field-independent term (which is constant with respect to field variations but depends on the RG scale $k$) requires special care within the Functional Renormalization Group (FRG) approach. In several instances, the constant term of the potential has no physical meaning. However, there are special cases where it receives important applications. In low dimensions ($d=1$), in a quantum mechanical model, this term is associated with the ground-state energy of the anharmonic oscillator. In higher dimensions ($d=4$), it is identical to the $\Lambda$ term of the Einstein equations and it plays a role in cosmic inflation. Thus, in statistical field theory, in flat space, the constant term could be associated with the free energy, while in curved space, it could be naturally associated with the cosmological constant. It is known that one has to use a subtraction method for the quantum anharmonic oscillator in $d=1$ to remove the $k^2$ term that appears in the RG flow in its high-energy (UV) limit in order to recover the correct results for the ground-state energy. The subtraction is needed because the Gaussian fixed point is missing in the RG flow once the constant term is included. However, if the Gaussian fixed point is there, no further subtraction is required. Here, we propose a subtraction method for $k^4$ and $k^2$ terms of the UV scaling of the RG equations for $d=4$ dimensions if the Gaussian fixed point is missing in the RG flow with the constant term. Finally, comments on the application of our results to cosmological models are provided.
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TL;DR: In this paper , the authors study the fiber bodies of puffed polytopes and give an explicit equation for the support function of the fiber body of a smooth convex body.
Abstract: Abstract In this paper we study the fiber bodies, that is the extension of the notion of fiber polytopes for more general convex bodies. After giving an overview of the properties of the fiber bodies, we focus on three particular classes of convex bodies. First we describe the strict convexity of the fiber bodies of the so called puffed polytopes. Then we provide an explicit equation for the support function of the fiber bodies of some smooth convex bodies. Finally we give a formula that allows to compute the fiber bodies of a zonoid with a particular focus on certain zonoids called discotopes. Throughout the paper we illustrate our results with detailed examples.
10 Oct 2022
TL;DR: In this paper , a model of associative storage and retrieval of compositional memories in an extended cortical network is considered, which is comprised of Potts units, which represent patches of cortex, interacting through long-range connections.
Abstract: Abstract We consider a model of associative storage and retrieval of compositional memories in an extended cortical network. Our model network is comprised of Potts units, which represent patches of cortex, interacting through long-range connections. The critical assumption is that a memory is composed of a limited number of items, each of which has a pre-established representation: storing a new memory only involves acquiring the connections, if novel, among the participating items. The model is shown to have a much lower storage capacity than when it stores simple unitary representations. It is also shown that an input from the hippocampus facilitates associative retrieval. When it is absent, it is advantageous to cue rare rather than frequent items. The implications of these results for emerging trends in empirical research are discussed.
TL;DR: In this paper , a kernel-based nonlinear method for dimension reduction with active subspaces is proposed for parametric computational fluid dynamics applications with the discontinuous Galerkin method.
Abstract: Nonlinear extensions to the active subspaces method have brought remarkable results for dimension reduction in the parameter space and response surface design. We further develop a kernel-based nonlinear method. In particular, we introduce it in a broader mathematical framework that contemplates also the reduction in parameter space of multivariate objective functions. The implementation is thoroughly discussed and tested on more challenging benchmarks than the ones already present in the literature, for which dimension reduction with active subspaces produces already good results. Finally, we show a whole pipeline for the design of response surfaces with the new methodology in the context of a parametric computational fluid dynamics application solved with the discontinuous Galerkin method.
TL;DR: In this article , the authors explore the connections between searches for long-lived particles (LLPs) at the LHC and early universe cosmology and show that the cosmologically interesting range ∆ N eff ~ 0 . 01 − 0 . 1 corresponds to LLP decay lengths in the mm to cm range.
Abstract: A bstract In this work we explore the intriguing connections between searches for long-lived particles (LLPs) at the LHC and early universe cosmology. We study the non-thermal production of ultra-relativistic particles (i.e. dark radiation) in the early universe via the decay of weak-scale LLPs and show that the cosmologically interesting range ∆ N eff ~ 0 . 01–0 . 1 corresponds to LLP decay lengths in the mm to cm range. These decay lengths lie at the boundary between prompt and displaced signatures at the LHC and can be comprehensively explored by combining searches for both. To illustrate this point, we consider a scenario where the LLP decays into a charged lepton and a (nearly) massless invisible particle. By reinterpreting searches for promptly decaying sleptons and for displaced leptons at both ATLAS and CMS we can then directly compare LHC exclusions with cosmological observables. We find that the CMB-S4 target value of ∆ N eff = 0 . 06 is already excluded by current LHC searches and even smaller values can be probed for LLP masses at the electroweak scale.