arXiv subjects

Marc Klinger

Publications and source records attributed to Marc Klinger.

9 recordsLinked to original sources

arXiv2025

A Theory of Backgrounds and Background Independence

In this note, we describe how the study of backgrounds for general quantum systems can be formulated in terms of the representation theory of abstract $C^*$ algebras. We illustrate our general framework through two example systems: superconductivity and perturbative quantum gravity. In both cases, spontaneously broken symmetries imply the existence of unitarily inequivalent Hilbert spaces that play the role of distinct backgrounds relative to which observables are measured. Background independence can be realized by gauging the broken symmetry; extending the algebra of observables for the theory to include new physical processes that intertwine between these disjoint representations. From the point of view of the background independent theory, different backgrounds have an interpretation as different vacuum expectation values of these intertwining operators. In superconductivity, the intertwiners are intimately related to the Josephson effect. In gravity, they are related to geometric fluctuations. We explain how this framework is connected to recent work on generalized symmetries and algebraic extensions. To this end, we close with some remarks about how the operator algebra of a closed universe may arise from a generalized symmetry associated with an algebraic extension of the causal wedge by appealing to subregion-subalgebra duality.

hep-th↗

arXiv2024

Lepto-Hadronic Scenarios for TeV Extensions of Gamma-Ray Burst Afterglow Spectra

Recent multi-wavelength observations of gamma-ray burst afterglows observed in the TeV energy range challenge the simplest Synchrotron Self-Compton (SSC) interpretation of this emission and are consistent with a single power-law component spanning over eight orders of magnitude in energy. To interpret this generic behaviour in the single-zone approximation without adding further free parameters, we perform an exhaustive parameter space study using the public, time-dependent, multi-messenger transport software AM3. This description accounts for the radiation from non-thermal protons and the lepto-hadronic cascade induced by pp- and p{\gamma}-interactions. We summarise the main scenarios which we have found (SSC, Extended-syn, Proton-syn, pp-cascade, and p{\gamma}-cascade), and discuss their advantages and limitations. We find that possible high-density environments, as may be typical for surrounding molecular cloud material, offer an alternative explanation for producing flat hard (source) spectra up to and beyond energies of 10 TeV.

astro-ph.HE↗

arXiv2023

AM$^3$: An Open-Source Tool for Time-Dependent Lepto-Hadronic Modeling of Astrophysical Sources

We present the AM$^3$ ("Astrophysical Multi-Messenger Modeling") software. AM$^3$ is a documented open source software that efficiently solves the coupled integro-differential equations describing the temporal evolution of the spectral densities of particles interacting in astrophysical environments, in-cluding photons, electrons, positrons, protons, neutrons, pions, muons, and neutrinos. The software has been extensively used to simulate the multi-wavelength and neutrino emission from active galactic nuclei (including blazars), gamma-ray bursts, and tidal disruption events. The simulations include all relevant non-thermal processes, namely synchrotron emission, inverse Compton scattering, photon-photon annihilation, proton-proton and proton-photon pion production, and photo-pair production. The software self-consistently calculates the full cascade of primary and secondary particles, including non-linear feedback processes and predictions in the time domain. It also allows to track separately the particle densities produced by means of each distinct interaction processes, including the different hadronic channels. With its efficient hybrid solver combining analytical and numerical techniques, AM$^3$ combines efficiency and accuracy at a user-adjustable level. We describe the technical details of the numerical framework and present three examples of applications to different astrophysical environments.

astro-ph.HE↗

arXiv2023

The Multiwavelength Picture of GRB 221009A's Afterglow

We present counts-level fits to the keV-GeV data of the early afterglow of the brightest gamma-ray burst detected to date, GRB 221009A. We discuss the complexity of the data reduction due to the unprecedented brightness and the location in the Galactic plane. We find the energy spectrum to be well described as a smoothly broken power law with a break around 10 keV and no indications for additional features towards GeV energies. An interpretation as synchrotron emission from forward-shock accelerated and subsequently cooled electrons yields three possible types of solutions: (1) a slow cooling solution with low magnetic fields (few percent of a Gauss) but poorly constrained minimum injected electron energy (<100 GeV), (2) a fast cooling solution with stronger magnetic fields (few percent to few Gauss) and minimum injected electron energy 10-100 GeV or (3) the transition between both regimes with low magnetic fields and minimum injected electron energy around 100 GeV. Limited statistics at GeV energies prevent conclusions extrapolating towards a cut-off or the onset of a new component at higher energies.

astro-ph.HE↗

arXiv2023

Multi-Camera Visual-Inertial Simultaneous Localization and Mapping for Autonomous Valet Parking

Localization and mapping are key capabilities for self-driving vehicles. In this paper, we build on Kimera and extend it to use multiple cameras as well as external (eg wheel) odometry sensors, to obtain accurate and robust odometry estimates in real-world problems. Additionally, we propose an effective scheme for closing loops that circumvents the drawbacks of common alternatives based on the Perspective-n-Point method and also works with a single monocular camera. Finally, we develop a method for dense 3D mapping of the free space that combines a segmentation network for free-space detection with a homography-based dense mapping technique. We test our system on photo-realistic simulations and on several real datasets collected on a car prototype developed by the Ford Motor Company, spanning both indoor and outdoor parking scenarios. Our multi-camera system is shown to outperform state-of-the art open-source visual-inertial-SLAM pipelines (Vins-Fusion, ORB-SLAM3), and exhibits an average trajectory error under 1% of the trajectory length across more than 8km of distance traveled (combined across all datasets). A video showcasing the system is available at: youtu.be/H8CpzDpXOI8.

cs.RO↗

arXiv2022

Probing the multiwavelength emission scenario of GRB 190114C

Multiwavelength observation of the gamma-ray burst, GRB 190114C, opens a new window for studying the emission mechanism of GRB afterglows. Its Very-High-Energy (VHE; $\gtrsim 100$ GeV) detection has motivated an inverse Compton interpretation for the emission, but this has not been tested. Here, we revisit the early afterglow emission from 68 to 180 seconds and perform the modeling likelihood analysis with the keV to TeV datasets. We compute for the first time the statistical preference in the combined synchrotron (syn) and synchrotron self-Compton (SSC) model over the syn-only model. In agreement with earlier analyses, between 68 and 110 seconds an unstable preference for the SSC model can be found, which can also be explained by systematic cross calibration effect between the included instruments. We conclude that there is no stable statistical preference for one of the two models.

astro-ph.HE↗

arXiv2022

On the Dynamics of Inference and Learning

Statistical Inference is the process of determining a probability distribution over the space of parameters of a model given a data set. As more data becomes available this probability distribution becomes updated via the application of Bayes' theorem. We present a treatment of this Bayesian updating process as a continuous dynamical system. Statistical inference is then governed by a first order differential equation describing a trajectory or flow in the information geometry determined by a parametric family of models. We solve this equation for some simple models and show that when the Cram\'{e}r-Rao bound is saturated the learning rate is governed by a simple $1/T$ power-law, with $T$ a time-like variable denoting the quantity of data. The presence of hidden variables can be incorporated in this setting, leading to an additional driving term in the resulting flow equation. We illustrate this with both analytic and numerical examples based on Gaussians and Gaussian Random Processes and inference of the coupling constant in the 1D Ising model. Finally we compare the qualitative behaviour exhibited by Bayesian flows to the training of various neural networks on benchmarked data sets such as MNIST and CIFAR10 and show how that for networks exhibiting small final losses the simple power-law is also satisfied.

cond-mat.dis-nn↗

arXiv2019

5.5 years multi-wavelength variability of Mrk 421: evidences of leptonic emission from the radio to TeV

Mrk 421 is a high-synchrotron-peaked blazar featuring bright and persistent GeV and TeV emission. We use the longest and densest ongoing unbiased observing campaign obtained at TeV and GeV energies during 5.5 years with the FACT telescope and the Fermi-LAT detector. The contemporaneous multi-wavelength observations were used to characterize the variability of the source and to constrain the underlying physical mechanisms. We study and correlate light curves obtained by nine different instruments from radio to gamma rays and found two significant results. The TeV and X-ray light curves are very well correlated with lag, if any, shorter than a day. The GeV light curve varies independently and accurately leads the variations observed at long wavelengths, in particular in the radio band. We find that the observations match the predictions of leptonic models and suggest that the physical conditions vary along the jet, when the emitting region moves outwards.

astro-ph.HE↗

arXiv2017

Observation of radio galaxies with HAWC

The High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory is an extensive air shower array located in Puebla, Mexico. The closest radio galaxy within the HAWC field of view, M87, has been detected in very high energies. In this work we report upper limits on the TeV {\gamma}-ray flux of the radio galaxy M87. At a distance of 16 Mpc, M87 is a supergiant elliptical galaxy located in the Virgo Cluster that has been observed from radio wavelengths to TeV {\gamma}-rays. Although a single-zone synchrotron self-Compton model has been successfully used to explain the spectral energy distribution of this source up to a few GeV, the {\gamma}-ray spectrum at TeV has been interpreted within different theoretical models. We discuss the implications of these upper limits on the photo-hadronic interactions, as well as the number of neutrino events expected in the IceCube neutrino telescope.

astro-ph.HE↗