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Heinrich Päs

Publications and source records attributed to Heinrich Päs.

At least 19 recordsLinked to original sources
arXiv2026

Tripartite entanglement of oscillating and decohering neutrinos

We study entanglement measures for oscillating neutrinos in the wave-packet formalism and confirm that an oscillating neutrino exhibits genuine tripartite entanglement and can be characterized as a member of the W class of states. We also show that this feature survives in the decoherence limit, and discuss the effect of CP phases on the entanglement. These findings provide new insights into the quantum nature of neutrino oscillations and their potential role in quantum information science, especially for neutrinos propagating large distances such as the astrophysical neutrinos observed at neutrino telescopes.

hep-ph↗
arXiv2025

Addendum: Fitting the DESI BAO Data with Dark Energy Driven by the Cohen-Kaplan-Nelson Bound

Motivated by the recent Year-2 data release of the DESI collaboration, we update our results on time-varying dark energy models driven by the Cohen-Kaplan-Nelson bound. The previously found preference of time-dependent dark energy models compared to $Λ$CDM is further strengthend by the new data release. For our particular models, we find that this preference increases up to $\approx 2.6\,σ$ depending on the used supernova dataset.

astro-ph.CO↗
arXiv2025

Potential of Neutrino Telescopes to Detect Quantum Gravity-Induced Decoherence in the Presence of Dark Fermions

We assess the potential of neutrino telescopes to discover quantum-gravity-induced decoherence effects modeled in the open-quantum system framework and with arbitrary numbers of active and dark fermion generations, such as particle dark matter or sterile neutrinos. The expected damping of neutrino flavor oscillation probabilities as a function of energy and propagation length thus encodes information about quantum gravity effects and the fermion generation multiplicity in the dark sector. We employ a public Monte-Carlo dataset provided by the IceCube Collaboration to model the detector response and estimate the sensitivity of IceCube to oscillation effects in atmospheric neutrinos induced by the presented model. Our findings confirm the potential of very-large-volume neutrino telescopes to test this class of models and indicate higher sensitivities for increasing numbers of dark fermions.

hep-ph↗
arXiv2025

Dark Energy Driven by the Cohen-Kaplan-Nelson Bound

In this work, we confront the bound on an ultraviolet cutoff (UV) of a quantum field theory (QFT) proposed by Cohen, Kaplan, and Nelson (CKN) with the latest results of the Dark Energy Spectroscopic Instrument (DESI). The former relates the UV cutoff with an infrared (IR) cutoff of the theory by excluding all states describing a black hole. Identifying now the IR cutoff with the Hubble horizon yields a time-varying contribution of the vacuum energy to the dark energy density of the universe. At the same time the DESI results in combination with other cosmological data point towards a preference of time-varying dark energy models over $Λ$CDM.

astro-ph.CO↗
arXiv2024

Neutrino Oscillations as a Gravitational Wave Detector?

Gravitational waves (GWs) can alter the neutrino propagation distance and thus affect neutrino oscillations. This can result in a complete disappearance of the oscillatory behavior that competes with other sources of neutrino decoherence. We develop a set of criteria that determines under which conditions neutrino oscillations are sensitive to this effect. We find that current or near future neutrino oscillation experiments are not sufficiently sensitive to coherent GW signals but may probe the stochastic gravitational wave background if the energy resolution improves drastically by several orders of magnitude.

hep-ph↗
arXiv2024

Fitting the DESI BAO Data with Dark Energy Driven by the Cohen-Kaplan-Nelson Bound

Gravity constrains the range of validity of quantum field theory. As has been pointed out by Cohen, Kaplan, and Nelson (CKN), such effects lead to interdependent ultraviolet (UV) and infrared (IR) cutoffs that may stabilize the dark energy of the universe against quantum corrections, if the IR cutoff is set by the Hubble horizon. As a consequence of the cosmic expansion, this argument implies a time-dependent dark energy density. In this paper we confront this idea with recent data from DESI BAO, Hubble and supernova measurements. We find that the CKN model provides a better fit to the data than the $Λ$CDM model and can compete with other models of time-dependent dark energy that have been studied so far.

astro-ph.CO↗
arXiv2024

UV/IR Mixing, Causal Diamonds and the Electroweak Hierarchy Problem

UV/IR Mixing is an umbrella term for phenomena in which high and low energy physics does not decouple as expected and may offer new perspectives on the electroweak hierarchy problem, i.e. the apparent unnaturally large hierarchy between the electroweak and the Planck scales. Based on how UV/IR mixing has been employed in the Cohen-Kaplan-Nelson bound and advocated as a solution to the cosmological constant problem, we argue that in the Higgs system causal diamonds replace the cosmic horizon as an infrared bound for effective field theory and show how this ansatz may help to explain the large hierarchy between the electroweak and the Planck scale.

hep-ph↗
arXiv2023

Light Sterile Neutrinos in the Early Universe: Effects of Altered Dispersion Relations and a coupling to Axion-Like Dark Matter

We investigate the cosmological consequences of light sterile neutrinos with altered dispersion relations (ADRs) and couplings to an ultra-light, axion-like scalar field. In particular we study the impact on the number of additional, light, fermionic degrees of freedom and primordial nucleosynthesis. While the ADR leads to a new potential term in the Hamiltonian, the coupling to the scalar field results in a time dependent, effective mass contribution. We solve the quantum kinetic equations (QKEs) for the neutrino density matrix and find that in certain parameter regions both new physics effects can individually yield a suppressed population of sterile neutrino species and the correct observed amount of helium in nucleosynthesis. Combining both effects opens up new patches of parameter space excluded by experimental bounds applying to models featuring only one of the effects.

hep-ph↗
arXiv2023

Radiative neutrino masses and the Cohen-Kaplan-Nelson bound

Recently, an increasing interest in UV/IR mixing phenomena has drawn attention to the range of validity of standard quantum field theory. Here we explore the consequences of such a limited range of validity in the context of radiative models for neutrino mass generation. We adopt an argument first published by Cohen, Kaplan and Nelson that gravity implies both UV and IR cutoffs, apply it to the loop integrals describing radiative corrections, and demonstrate that this effect has significant consequences for the parameter space of radiative neutrino mass models.

hep-ph↗
arXiv2022

Quantum Gravitational Decoherence in the 3 Neutrino Flavor Scheme

In many theories of quantum gravity quantum fluctuations of spacetime may serve as an environment for decoherence. Here we study quantum-gravitational decoherence of high energy astrophysical neutrinos in the presence of fermionic dark sectors and for a realistic three neutrino scenario. We show how violation of global symmetries expected to arise in quantum gravitational interactions provides a possibility to pin down the number of dark matter fermions in the universe. Furthermore, we predict the expected total neutrino flux and flavor ratios at experiments depending on the flavor composition at the source.

hep-ph↗
arXiv2022

Searching New Particles at Neutrino Telescopes with Quantum-Gravitational Decoherence

We discuss the interplay of wave packet decoherence and decoherence induced by quantum gravity via interactions with spacetime foam for high energy astrophysical neutrinos. In this context we point out a compelling consequence of the expectation that quantum gravity should break global symmetries, namely that quantum-gravity induced decoherence may not only be the most sensitive probe for quantum properties of spacetime, but also can provide both a powerful tool for the search for new particles, including totally decoupled backgrounds interacting only gravitationally, and at the same time a window into the intricacies of black hole information processing.

hep-ph↗
arXiv2021

Fermionic Singlet Dark Matter in One-Loop Solutions to the $R_K$ Anomaly: A Systematic Study

We study the dark matter phenomenology of Standard Model extensions addressing the reported anomaly in the $R_K$ observable at one-loop. The article covers the case of fermionic singlet DM coupling leptophilically, quarkphilically or amphiphilically to the SM. The setup utilizes a large coupling of the new particle content to the second lepton generation to explain the $R_K$ anomaly, which in return tends to diminish the dark matter relic density. Further, dark matter direct detection experiments provide stringent bounds even in cases where the dark matter candidate only contributes a small fraction of the observed dark matter energy density. In fact, direct detection rules out all considered models as an explanation for the $R_K$ anomaly in the case of Dirac dark matter. Conversely, for Majorana dark matter, the $R_K$ anomaly can be addressed in agreement with direct detection in coannihilation scenarios. For leptophilic dark matter this region only exists for $M_\text{DM} \lesssim 1000 \, \mathrm{GeV}$ and dark matter is underabundant. Quarkphilic and amphiphilic scenarios even provide narrow regions of parameter space where the observed relic density can be reproduced while offering an explanation to $R_K$ in agreement with direct detection experiments.

hep-ph↗
arXiv2021

Sterile Neutrinos with Altered Dispersion Relations as an Explanation for Neutrino Anomalies

Recently the MiniBooNE Collaboration has confirmed its anomalous excess in (anti)muon- to (anti)electron-neutrino oscillation data. Combined with long-standing results from the LSND experiment this amounts to a 6.1 sigma evidence for new physics beyond the Standard Model. In this paper we develop a framework with 3 active and 3 sterile neutrinos with altered dispersion relations that provides a mechanism to explain these anomalies without being in conflict with the absence of anomalous neutrino disappearance in other neutrino oscillation experiments.

hep-ph↗
arXiv2020

Flipped Quartification and a composite $b$-quark

An alternative "flipped" version of the quartification model is obtained by rearrangement of the particle assignments. The model has two standard (trinification) families and one flipped quartification family. An interesting phenomenological implication is that the model allows for a composite $b$-quark.

hep-ph↗
arXiv2019

Majoron Dark Matter and Constraints on the Majoron-Neutrino Coupling

We revisit a singlet Majoron model in which neutrino masses arise from the spontaneous violation of lepton number. If the Majoron obtains a mass of order MeV, it can play the role of dark matter. We discuss constraints on the couplings of the massive Majoron with masses of order MeV to neutrinos from supernova data. In the dense supernova core, Majoron-emitting neutrino annihilations are allowed and can change the signal of a supernova. Based on the observation of SN1987A, we exclude a large range of couplings from the luminosity and the deleptonization arguments, taking the effect of the background medium into account. If the Majoron mass does not exceed the Q-value of the experiment, the neutrino-Majoron couplings allow for neutrinoless double beta decay with Majoron emission. We derive constraints on the couplings for a Majoron mass of order MeV based on the phase space suppression and the diminishing signal-to-background ratio due to the Majoron mass. The combination of constraints from astrophysics and laboratory experiments excludes a large range of neutrino-Majoron couplings in the mass range of intererest for Majoron dark matter.

hep-ph↗
arXiv2019

Physics Beyond the Multiverse - Naturalness and the Quest for a Fundamental Theory

Finetuning and Naturalness are extra-empirical theory assessments that reflect our expectation how scientific theories should provide an intuitive understanding about the foundations underlying the observed phenomena. Recently, the absence of new physics at the LHC and the theoretical evidence for a multiverse of alternative physical realities, predicted by our best fundamental theories, have casted doubts about the validity of these concepts. In this essay we argue that the discussion about Finetuning should not predominantly concentrate on the desired features a fundamental theory is expected to have, but rather on the question what a theory needs to qualify as fundamental in the first place. By arguing that a fundamental description of the Universe should possess zero entropy, we develop a 'holistic' concept for the most fundamental layer of reality: The fundamental description of the Universe is the Universe itself, understood as an entangled quantum state. Adopting a universal applicability of quantum mechanics, in this framework the behavior of subsystems can be understood as the perspectival experience of an entangled quantum Universe perceived through the "lens of decoherence". In this picture the fundamental reality is non-local, and finetuned coincidences in effective theories may be understood in a way similar to EPR-correlations. This notion provides a fresh view on the topic of Naturalness and Finetuning since it suggests that Finetuning problems and hints for anthropic explanations are an artefact of theories building up on subsystems rather than on the fundamental description. Recent work in quantum gravity aiming at an understanding of spacetime geometry from entanglement entropy could be interpreted as a first sign of such a paradigm shift.

physics.hist-ph↗
arXiv2018

Scalar Dark Matter, GUT baryogenesis and Radiative neutrino mass

We investigate an interesting correlation among dark matter phenomenology, neutrino mass generation and GUT baryogenesis, based on the scotogenic model. The model contains additional right-handed neutrinos $N$ and a second Higgs doublet $Φ$, both of which are odd under an imposed $Z_2$ symmetry. The neutral component of $Φ$, i.e. the lightest of the $Z_2$-odd particles, is the dark matter candidate. Due to a Yukawa coupling involving $Φ$, $N$ and the Standard Model leptons, the lepton asymmetry is converted into the dark matter asymmetry so that a non-vanishing $B-L$ asymmetry can arise from $(B-L)$-conserving GUT baryogenesis, leading to a nonzero baryon asymmetry after the sphalerons decouple. On the other hand, $Φ$ can also generate neutrino masses radiatively. In other words, the existence of $Φ$ as the dark matter candidate resuscitates GUT baryogenesis and realizes neutrino masses.

hep-ph↗