# Publications by Joseph Conlon

## A note on brane inflation

Acta Physica Polonica B, Proceedings Supplement 13 (2020) 231-235

JP Conlon

© 2020 Jagellonian University. All rights reserved. This short note emphasises a potential tension between string models of inflation based on systems of branes and antibranes and the spectrum of strings in curved space, in particular the requirement that the leading Regge trajectory extends to the Planck scale allowing for the conventional string theory UV completion of gravity.

## Physics potential of the International Axion Observatory (IAXO)

Journal of Cosmology and Astroparticle Physics IOP Publishing 2019 (2019) 47

E Armengaud, D Attie, S Basso, P Brun, N Bykovskiy, JM Carmona, JF Castel, S Cebrian, M Cicoli, A Dudarev, E Ferrer-Ribas, G Galanti, L Garrido, B Lakic, P Laurent, G Luzon, MCD Marsh, C Mergalejo, H Mirallas, V Pantuev, T Papaevangelou, J Salvado, S Schmidt, M Schott, F Tavecchio

We review the physics potential of a next generation search for solar axions: the International Axion Observatory (IAXO). Endowed with a sensitivity to discover axion-like particles (ALPs) with a coupling to photons as small as gaγ ∼ 10−12 GeV−1 , or to electrons gae ∼10−13, IAXO has the potential to find the QCD axion in the 1 meV∼1 eV mass range where it solves the strong CP problem, can account for the cold dark matter of the Universe and be responsible for the anomalous cooling observed in a number of stellar systems. At the same time, IAXO will have enough sensitivity to detect lower mass axions invoked to explain: 1) the origin of the anomalous “transparency” of the Universe to gamma-rays, 2) the observed soft X-ray excess from galaxy clusters or 3) some inflationary models. In addition, we review string theory axions with parameters accessible by IAXO and discuss their potential role in cosmology as Dark Matter and Dark Radiation as well as their connections to the above mentioned conundrums.

## Constraints on Massive Axion-Like Particles from X-ray Observations of NGC1275

Monthly Notices of the Royal Astronomical Society (2018)

L Chen, JP Conlon

## The de Sitter swampland conjecture and supersymmetric AdS vacua

International Journal of Modern Physics A World Scientific Publishing (2018)

JP Conlon

It has recently been conjectured that string theory does not admit de Sitter critical points. This note points out that in several cases, including KKLT or racetrack models, this statement is equivalent to the absence of supersymmetric Minkowski or AdS solutions. This equivalence arises from establishing the positivity of the potential in a large-radius limit, requiring a turnover of the potential before reaching an AdS vacuum. For example, this conjecture is incompatible with the simplest 1-modulus KKLT AdS supersymmetric solution.

## Can black hole superradiance be induced by galactic plasmas?

Physics Letters B Elsevier BV (2018)

JP Conlon, CAR Herdeiro

Highly spinning Kerr black holes with masses $M = 1 - 100\ M_{\odot}$ are subject to an efficient superradiant instability in the presence of bosons with masses $\mu \sim 10^{-10} - 10^{-12}\ {\rm eV}$. We observe that this matches the effective plasma-induced photon mass in diffuse galactic or intracluster environments ($\omega_{\rm pl} \sim 10^{-10} - 10^{-12}\ {\rm eV}$). This suggests that bare Kerr black holes within galactic or intracluster environments, possibly even including the ones produced in recently observed gravitational wave events, are unstable to formation of a photon cloud that may contain a significant fraction of the mass of the original black hole. At maximal efficiency, the instability timescale for a massive vector is milliseconds, potentially leading to a transient rate of energy extraction from a black hole in principle as large as $\sim 10^{55} \ {\rm erg \, s}^{-1}$. We discuss possible astrophysical effects this could give rise to, including a speculative connection to Fast Radio Bursts.

## Constraints on axion-like particles from non-observation of spectral modulations for X-ray point sources

Journal of Cosmology and Astroparticle Physics IOP Publishing 2017 (2017) 005

J Conlon, F Day, N Jennings, S Krippendorf, M Rummel

We extend previous searches for X-ray spectral modulations induced by ALP-photon conversion to a variety of new sources, all consisting of quasars or AGNs located in or behind galaxy clusters. We consider a total of seven new sources, with data drawn from the Chandra archive. In all cases the spectrum is well fit by an absorbed power-law with no evidence for spectral modulations, allowing constraints to be placed on the ALP-photon coupling parameter $g_{a\gamma\gamma}$. Two sources are particularly good: the Seyfert galaxy 2E3140 in A1795 and the AGN NGC3862 within the cluster A1367, leading to 95\% bounds for light ALPs ($m_a \lesssim 10^{-12} {\rm eV}$) of $g_{a\gamma\gamma} \lesssim 1.5 \times 10^{-12} {\rm GeV}^{-1}$ and $g_{a\gamma\gamma} \lesssim 2.4 \times 10^{-12} {\rm GeV}^{-1}$ respectively.

## Consistency of Hitomi, XMM-Newton, and Chandra 3.5 keV data from Perseus

PHYSICAL REVIEW D 96 (2017) ARTN 123009

JP Conlon, F Day, N Jennings, S Krippendorf, M Rummel

## Constraints on Axion-Like Particles from X-ray Observations of NGC1275

Astrophysical Journal IOP Publishing 847 (2017) 101-

M Berg, J Conlon, F Day, N Jennings, S Krippendorf, AJ Powell, M Rummel

Axion-like particles (ALPs) can induce localised oscillatory modulations in the spectra of photon sources passing through astrophysical magnetic fields. Ultra-deep Chandra observations of the Perseus cluster contain over $5 \times 10^5$ counts from the AGN of the central cluster galaxy NGC1275, and represent a dataset of extraordinary quality for ALP searches. We use this dataset to search for X-ray spectral irregularities from the AGN. The absence of irregularities at the O(30%) level allows us to place leading constraints on the ALP-photon mixing parameter $g_{a\gamma\gamma} \lesssim 1.4 - 4.0 \times 10^{-12} {\rm GeV}^{-1}$ for $m_a \lesssim 10^{-12}$ eV, depending on assumptions on the magnetic field realisation along the line of sight.

## Galaxy cluster thermal x-ray spectra constrain axionlike particles

Physical Review D American Physical Society 93 (2016) 123526

J Conlon, AJ Powell, MCD Marsh

Axion-like particles (ALPs) and photons inter-convert in the presence of a magnetic field. At keV energies in the environment of galaxy clusters, the conversion probability can become unsuppressed for light ALPs. Conversion of thermal X-ray photons into ALPs can introduce a step-like feature into the cluster thermal bremsstrahlung spectrum, and we argue that existing X-ray data on galaxy clusters should be sufficient to extend bounds on ALPs in the low-mass region ma . 1 × 10−12 eV down to M ∼ 7 × 1011 GeV, and that for 1011 GeV &lt; M . 1012 GeV light ALPs give rise to interesting and unique observational signatures that may be probed by existing and upcoming Xray (and potentially X-ray polarisation) observations of galaxy clusters.

## Axion decay constants away from the lamppost

Journal of High Energy Physics Springer Berlin Heidelberg 85 (2016)

J Conlon, S Krippendorf

It is unknown whether a bound on axion field ranges exists within quantum gravity. We study axion field ranges using extended supersymmetry, in particular allowing an analysis within strongly coupled regions of moduli space. We apply this strategy to Calabi-Yau compactifications with one and two Kähler moduli. We relate the maximally allowable decay constant to geometric properties of the underlying Calabi-Yau geometry. In all examples we find a maximal field range close to the reduced Planck mass (with the largest field range being 3.25 MP). On this perspective, field ranges relate to the intersection and instanton numbers of the underlying Calabi-Yau geometry.

## The What and Why of Moduli

in Advanced Series on Directions in High Energy Physics, WORLD SCIENTIFIC (2015) 11-22

J Conlon

## A 3.55 keV line from DM -> a -> gamma predictions for cool-core and non-cool-core clusters

JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS (2015) ARTN 019

JP Conlon, AJ Powell

## ALP conversion and the soft X-ray excess in the outskirts of the Coma cluster

JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS (2015) ARTN 011

D Kraljic, M Rummel, JP Conlon

## Observational consistency and future predictions for a 3.5 keV ALP to photon line

JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS (2015) ARTN 013

PD Alvarez, JP Conlon, FV Day, MCD Marsh, M Rummel

## 3.55 keV photon lines from axion to photon conversion in the Milky Way and M31

JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS (2014) ARTN 033

JP Conlon, FV Day

## Soft X-ray excess in the Coma cluster from a Cosmic Axion Background

JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS (2014) ARTN 026

S Angus, JP Conlon, MCD Marsh, AJ Powell, LT Witkowski

## A note on the magnitude of the flux superpotential

JOURNAL OF HIGH ENERGY PHYSICS (2014) ARTN 027

M Cicoli, JP Conlon, A Maharana, F Quevedo

## 3.55 keV photon line and its morphology from a 3.55 keV axionlike particle line

PHYSICAL REVIEW D 90 (2014) ARTN 023540

M Cicoli, JP Conlon, MCD Marsh, M Rummel

## Excess Astrophysical Photons from a 0.1–1 keV Cosmic Axion Background

Physics Review Letters 111 (2013) 15130

J Conlon, MCD Marsh

## Soft supersymmetry breaking in anisotropic LARGE volume compactifications

JOURNAL OF HIGH ENERGY PHYSICS (2013) ARTN 071

S Angus, JP Conlon