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M. Schiffer

Publications and source records attributed to M. Schiffer.

7 recordsLinked to original sources
arXiv2025

Exploring Quantum Spacetime with Topological Data Analysis

In a novel application of the tools of topological data analysis (TDA) to nonperturbative quantum gravity, we introduce a new class of observables that allows us to assess whether quantum spacetime really resembles a ``quantum foam" near the Planck scale. The key idea is to investigate the Betti numbers of coarse-grained path integral histories, regularized in terms of dynamical triangulations, as a function of the coarse-graining scale. In two dimensions our analysis exhibits the well-known fractal structure of Euclidean quantum gravity.

hep-th↗
arXiv2025

Quantum Gravity and Effective Topology

We introduce a new methodology to characterize properties of quantum spacetime in a strongly quantum-fluctuating regime, using tools from topological data analysis. Starting from a microscopic quantum geometry, generated nonperturbatively in terms of dynamical triangulations (DT), we compute the Betti numbers of a sequence of coarse-grained versions of the geometry as a function of the coarse-graining scale, yielding a characteristic ``topological finger print". We successfully implement this methodology in Lorentzian and Euclidean 2D quantum gravity, defined via lattice quantum gravity based on causal and Euclidean DT, yielding different results. Effective topology also enables us to formulate necessary conditions for the recovery of spacetime symmetries in a classical limit.

hep-th↗
arXiv2024

A decomposition-based approach for large-scale pickup and delivery problems

With the advent of self-driving cars, experts envision autonomous mobility-on-demand services in the near future to cope with overloaded transportation systems in cities worldwide. Efficient operations are imperative to unlock such a system's maximum improvement potential. Existing approaches either consider a narrow planning horizon or ignore essential characteristics of the underlying problem. In this paper, we develop an algorithmic framework that allows the study of very large-scale pickup and delivery routing problems with more than 20 thousand requests, which arise in the context of integrated request pooling and vehicle-to-request dispatching. We conduct a computational study and present comparative results showing the characteristics of the developed approaches. Furthermore, we apply our algorithm to related benchmark instances from the literature to show the efficacy. Finally, we solve very large-scale instances and derive insights on upper-bound improvements regarding fleet sizing and customer delay acceptance from a practical perspective.

math.OC↗
arXiv2014

Does the Cosmological Expansion Change Local Dynamics?

It is well a known fact that the Newtonian description of dynamics within Galaxies for its known matter content is in disagreement with the observations as the acceleration approaches $a_0 \approx 1.2 \times 10^{-10}m/s^2$ (slighter larger for clusters). Both the Dark Matter scenario and Modified Gravity Theories (MGT) fails to explain the existence of such an acceleration scale. Motivated by the closeness of this acceleration scale and $c H_0\approx 10^{-9} h$ $ m/s^2$, we analyse whether this coincidence might have a Cosmological origin for scalar-tensor and spinor-tensor theories, performing detailed calculations for perturbations that represent the local matter distribution on the top of the cosmological background. Then, we solve the field equations for these perturbations in a power series in the present value of the Hubble constant. As we shall see, for both theories the power expansion contains only even powers in the Hubble constant, a fact that renders the cosmological expansion irrelevant for the local dynamics. At last, we show what a difference a theory predicting linear terms in H makes in the local dynamics.

gr-qc↗
arXiv1997

Sonoluminescence: The Superradiance Paradigm

In this article we explain sonoluminescence from ideas borrowed from superradiance. The model has no free parameters and the predicted energies of quanta agree with experiment. It also hints why noble gases play a pivotal role in the effect.

quant-ph↗
arXiv1993

Is it possible to recover information from the black-hole radiation?

In the framework of communication theory, we analyse the gedanken experiment in which beams of quanta bearing information are flashed towards a black hole. We show that stimulated emission at the horizon provides a correlation between incoming and outgoing radiations consisting of bosons. For fermions, the mechanism responsible for the correlation is the Fermi exclusion principle. Each one of these mechanisms is responsible for the a partial transfer of the information originally coded in the incoming beam to the black--hole radiation. We show that this process is very efficient whenever stimulated emission overpowers spontaneous emission (bosons). Thus, black holes are not `ultimate waste baskets of information'.

hep-th↗