arXiv subjects

Aidan Reilly

Publications and source records attributed to Aidan Reilly.

5 recordsLinked to original sources

arXiv2025

Hydrogen 21 cm Constraints on the Photon's Spin Scale

We explore the fundamental but untested possibility that the photon is a continuous spin particle (CSP) with a small but non-zero spin Casimir $ρ$. When $ρ\neq 0$, the familiar polarization modes of the photon transform non-trivially under Lorentz boosts, leading to deviations from familiar QED. Surprisingly, these deviations are strongest at low energy, but smoothly vanish in the $ρ\rightarrow 0$ limit. In this letter, we compute corrections to the hydrogen 21cm transition rate, which is expected to be particularly sensitive given the small hyperfine energy splitting $ω$. We find deviations from QED $\propto ρ^2 α^2/ω^2$ at leading order, suggesting experimental constraints $ρ\lesssim 1$ meV. Building on this work, we expect that a range of other atomic, molecular, or condensed matter systems could be used to provide even more stringent tests of $ρ$ in electromagnetic interactions.

hep-ph↗

arXiv2025

Probing "Continuous Spin" QED with Rare Atomic Transitions

An intriguing and elementary possibility is that familiar massless particles like the photon could be "continuous spin" particles (CSP) with a small but non-zero spin Casimir $ρ$. In this case, the familiar two polarization states of the photon are accompanied by an infinite tower of integer spaced helicity modes, with couplings dictated entirely by Lorentz symmetry and the parameter $ρ$. We present a formalism for computing bound state atomic transitions for scalar QED when $ρ\neq 0$, employing path integral methods not often used for bound state computations, but that readily generalize to the CSP case. We compute several illustrative amplitudes and show that $ρ\neq 0$ opens new decay channels for atomic transitions with rates controlled by $ρα/ω$ for transition frequency $ω$. These new channels can appreciably modify the rates of "forbidden" transitions. For example, the lifetime of the hydrogen $2s$ state would be affected at $O(1)$ for $ρ\sim 0.1$ eV, suggesting new directions for fundamental tests of QED in laboratory experiments.

hep-ph↗

arXiv2024

Quantum tensor network algorithms for evaluation of spectral functions on quantum computers

We investigate quantum algorithms derived from tensor networks to simulate the static and dynamic properties of quantum many-body systems. Using a sequentially prepared quantum circuit representation of a matrix product state (MPS) that we call a quantum tensor network (QTN), we demonstrate algorithms to prepare ground and excited states on a quantum computer and apply them to molecular nanomagnets (MNMs) as a paradigmatic example. In this setting, we develop two approaches for extracting the spectral correlation functions measured in neutron scattering experiments: (a) a generalization of the SWAP test for computing wavefunction overlaps and, (b) a generalization of the notion of matrix product operators (MPOs) to the QTN setting which generates a linear combination of unitaries. The latter method is discussed in detail for translationally invariant spin-half systems, where it is shown to reduce the qubit resource requirements compared with the SWAP method, and may be generalized to other systems. We demonstrate the versatility of our approaches by simulating spin-1/2 and spin-3/2 MNMs, with the latter being an experimentally relevant model of a Cr$^{3+}_8$ ring. Our approach has qubit requirements that are independent of the number of constituents of the many-body system and scale only logarithmically with the bond dimension of the MPS representation, making them appealing for implementation on near-term quantum hardware with mid-circuit measurement and reset.

quant-ph↗

arXiv2023

Ultraviolet Running Constraints on Low Mass Dark Sectors

We analyze the UV breakdown of Sub-GeV dark matter models that live in a new, dark U(1) sector. Many of these models include a scalar field, which is either the dark matter itself or a dark Higgs field that generates mass terms for the dark matter particle via spontaneous symmetry breaking. A quartic self coupling of this scalar field is generically allowed, and we show that its running is largely governed by the strength of the U(1) gauge field, $α_D$. Furthermore, it consistently has a lower Landau pole than the gauge coupling. Link fields, which couple to both the dark sector and the Standard Model (SM), connect these Landau poles to constraints on SM charged particles. Current LHC constraints on link fields are compatible with $α_D \lesssim 0.5 - 1$ for most of the mass range in most models, while smaller values, $α_D \lesssim 0.15$, are favored for Majorana DM.

hep-ph↗

arXiv2019

Six Dimensional Streaming Algorithm for Cluster Finding in N-Body Simulations

Cosmological N-body simulations are crucial for understanding how the Universe evolves. Studying large-scale distributions of matter in these simulations and comparing them to observations usually involves detecting dense clusters of particles called "halos,'' which are gravitationally bound and expected to form galaxies. However, traditional cluster finders are computationally expensive and use massive amounts of memory. Recent work by Liu et al (Liu et al. (2015)) showed the connection between cluster detection and memory-efficient streaming algorithms and presented a halo finder based on heavy hitter algorithm. Later, Ivkin et al. (Ivkin et al. (2018)) improved the scalability of suggested streaming halo finder with efficient GPU implementation. Both works map particles' positions onto a discrete grid, and therefore lose the rest of the information, such as their velocities. Therefore, two halos travelling through each other are indistinguishable in positional space, while the velocity distribution of those halos can help to identify this process which is worth further studying. In this project we analyze data from the Millennium Simulation Project (Springel et al. (2005)) to motivate the inclusion of the velocity into streaming method we introduce. We then demonstrate a use of suggested method, which allows one to find the same halos as before, while also detecting those which were indistinguishable in prior methods.

astro-ph.GA↗