# Publications by Joseph Conlon

## A note on the magnitude of the flux superpotential

JOURNAL OF HIGH ENERGY PHYSICS (2014) ARTN 027

## A 3.55 keV Photon Line and its Morphology from a 3.55 keV ALP Line

ArXiv (2014)

Galaxy clusters can efficiently convert axion-like particles (ALPs) to photons. We propose that the recently claimed detection of a 3.55--3.57 keV line in the stacked spectra of a large number of galaxy clusters and the Andromeda galaxy may originate from the decay of either a scalar or fermionic $7.1$ keV dark matter species into an axion-like particle (ALP) of mass $m_{a} \lesssim 6\cdot 10^{-11}~{\rm eV}$, which subsequently converts to a photon in the cluster magnetic field. In contrast to models in which the photon line arises directly from dark matter decay or annihilation, this can explain the anomalous line strength in the Perseus cluster. As axion-photon conversion scales as $B^2$ and cool core clusters have high central magnetic fields, this model can also explains the observed peaking of the line emission in the cool cores of the Perseus, Ophiuchus and Centaurus clusters, as opposed to the much larger dark matter halos. We describe distinctive predictions of this scenario for future observations.

## Superpotential de-sequestering in string models

Journal of High Energy Physics **2013** (2013)

Non-perturbative superpotential cross-couplings between visible sector matter and Kähler moduli can lead to significant flavour-changing neutral currents in compactifications of type IIB string theory. Here, we compute corrections to Yukawa couplings in orbifold models with chiral matter localised on D3-branes and non-perturbative effects on distant D7-branes. By evaluating a threshold correction to the D7-brane gauge coupling, we determine conditions under which the non-perturbative corrections to the Yukawa couplings appear. The flavour structure of the induced Yukawa coupling generically fails to be aligned with the tree-level flavour structure. We check our results by also evaluating a correlation function of two D7-brane gauginos and a D3-brane Yukawa coupling. Finally, by calculating a string amplitude between n hidden scalars and visible matter we show how non-vanishing vacuum expectation values of distant D7-brane scalars, if present, may correct visible Yukawa couplings with a flavour structure that differs from the tree-level flavour structure. © 2013 SISSA, Trieste, Italy.

## Loop corrections to Delta N_eff in large volume models

ArXiv (2013)

In large volume models reheating is driven by the decays of the volume modulus to the visible sector, while the decays to its axion partners result in dark radiation. In this article we discuss the impact of loop corrections on the only model-independent visible decay channel: the decay into Higgs pairs via a Giudice-Masiero term. Including such radiative effects leads to a more precise determination of the relative fraction of dark radiation, since by contrast all loop corrections to the volume axion decay mode are Planck suppressed. Assuming an MSSM spectrum and that the Giudice-Masiero coupling is fixed at the string scale by a shift symmetry in the Higgs sector, we arrive at a prediction for the effective number of neutrinos. The result turns out to be too large to be consistent with data, highly disfavouring the minimal model.

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

Physics Review Letters **111** (2013) 15130

## The Cosmophenomenology of Axionic Dark Radiation

ArXiv (2013)

Relativistic axions are good candidates for the dark radiation for which there are mounting observational hints. The primordial decays of heavy fields produce axions which are ultra-energetic compared to thermalised matter and inelastic axion-matter scattering can occur with $E_{CoM} \gg T_{\gamma}$, thus accessing many interesting processes which are otherwise kinematically forbidden in standard cosmology. Axion-photon scattering into quarks and leptons during BBN affects the light element abundances, and bounds on overproduction of $^4$He constrain a combination of the axion decay constant and the reheating temperature. For supersymmetric models, axion scattering into visible sector superpartners can give direct non-thermal production of dark matter at $T_{\gamma} \ll T_{freezeout}$. Most axions --- or any other dark radiation candidate from modulus decay --- still linger today as a Cosmic Axion Background with $E_{axion} \sim \mathcal{O}(100) eV$, and a flux of $\sim 10^6 cm^{-2} s^{-1}$.

## Searching for a 0.1-1 keV Cosmic Axion Background

ArXiv (2013)

Primordial decays of string theory moduli at z \sim 10^{12} naturally generate a dark radiation Cosmic Axion Background (CAB) with 0.1 - 1 keV energies. This CAB can be detected through axion-photon conversion in astrophysical magnetic fields to give quasi-thermal excesses in the extreme ultraviolet and soft X-ray bands. Substantial and observable luminosities may be generated even for axion-photon couplings \ll 10^{-11} GeV^{-1}. We propose that axion-photon conversion may explain the observed excess emission of soft X-rays from galaxy clusters, and may also contribute to the diffuse unresolved cosmic X-ray background. We list a number of correlated predictions of the scenario.

## Dark radiation in LARGE volume models

PHYSICAL REVIEW D **87** (2013) ARTN 043520

## Cosmological natural selection and the purpose of the universe

Complexity **18** (2013) 48-56

The cosmological natural selection (CNS) hypothesis holds that the fundamental constants of nature have been fine-tuned by an evolutionary process in which universes produce daughter universes via the formation of black holes. Here, we formulate the CNS hypothesis using standard mathematical tools of evolutionary biology. Specifically, we capture the dynamics of CNS using Price's equation, and we capture the adaptive purpose of the universe using an optimization program. We establish mathematical correspondences between the dynamics and optimization formalisms, confirming that CNS acts according to a formal design objective, with successive generations of universes appearing designed to produce black holes. © 2013 Wiley Periodicals, Inc.

## Soft supersymmetry breaking in anisotropic LARGE volume compactifications

JOURNAL OF HIGH ENERGY PHYSICS (2013) ARTN 071

## Brane-Antibrane Backreaction in Axion Monodromy Inflation

ArXiv (2011)

We calculate the interaction potential between D5 and anti-D5 branes wrapping distant but homologous 2-cycles. The interaction potential is logarithmic in the separation radius and does not decouple at infinity. We show that logarithmic backreaction is generic for 5-branes wrapping distant but homologous 2-cycles, and we argue that this destabilises models of axion monodromy inflation involving NS5 brane-antibrane pairs in separate warped throats towards an uncontrolled region.

## Supersymmetric Radiative Flavour

ArXiv (2011)

We examine possibilities for the radiative generation of the Yukawa couplings and flavour structure in supersymmetric models in the supersymmetric phase. Not withstanding the non-renormalisation of the Wilsonian superpotential, this can occur through the 2-loop vertex renormalisation of the physical 1PI couplings. We describe this effect and construct models in which this occurs. For models attempting to reproduce the full flavour structure of the Standard Model, we analyse the tension between such models and constraints from low-energy flavour observables. We note that the tension is weakest for the case of generating Dirac neutrino masses.

## Quantum Gravity Constraints on Inflation

ArXiv (2012)

We study quantum gravity constraints on inflationary model building. Our approach is based on requiring the entropy associated to a given inflationary model to be less than that of the de Sitter entropy. We give two prescriptions for determining the inflationary entropy, based on either `bits per unit area' or entanglement entropy. The existence of transPlanckian flat directions, necessary for large tensor modes in the CMB, correlates with an inflationary entropy greater than that allowed by de Sitter space. Independently these techniques also constrain or exclude de Sitter models with large-rank gauge groups and high UV cutoffs, such as racetrack inflation or the KKLT construction.

## Scattering and Sequestering of Blow-Up Moduli in Local String Models

ArXiv (2011)

We study the scattering and sequestering of blow-up fields - either local to or distant from a visible matter sector - through a CFT computation of the dependence of physical Yukawa couplings on the blow-up moduli. For a visible sector of D3-branes on orbifold singularities we compute the disk correlator < \tau_s^{(1)} \tau_s^{(2)} ... \tau_s^{(n)} \psi \psi \phi > between orbifold blow-up moduli and matter Yukawa couplings. For n = 1 we determine the full quantum and classical correlator. This result has the correct factorisation onto lower 3-point functions and also passes numerous other consistency checks. For n > 1 we show that the structure of picture-changing applied to the twist operators establishes the sequestering of distant blow-up moduli at disk level to all orders in \alpha'. We explain how these results are relevant to suppressing soft terms to scales parametrically below the gravitino mass. By giving vevs to the blow-up fields we can move into the smooth limit and thereby derive CFT results for the smooth Swiss-cheese Calabi-Yaus that appear in the Large Volume Scenario.

## Moduli-Induced Vacuum Destabilisation

ArXiv (2010)

We look for ways to destabilise the vacuum. We describe how dense matter environments source a contribution to moduli potentials and analyse the conditions required to initiate either decompactification or a local shift in moduli vevs. We consider astrophysical objects such as neutron stars as well as cosmological and black hole singularities. Regrettably neutron stars cannot destabilise realistic Planck coupled moduli, which would require objects many orders of magnitude denser. However gravitational collapse, either in matter-dominated universes or in black hole formation, inevitably leads to a destabilisation of the compact volume causing a super-inflationary expansion of the extra dimensions.

## Anomaly Mediation in Superstring Theory

ArXiv (2010)

We study anomaly mediated supersymmetry breaking in type IIB string theory and use our results to test the supergravity formula for anomaly mediated gaugino masses. We compute 1-loop gaugino masses for models of D3-branes on orbifold singularities with 3-form fluxes by calculating the annulus correlator of 3-form flux and two gauginos in the zero momentum limit. Consistent with supergravity expectations we find both anomalous and running contributions to 1-loop gaugino masses. For background Neveu-Schwarz H-flux we find an exact match with the supergravity formula. For Ramond-Ramond flux there is an off-shell ambiguity that precludes a full matching. The anomaly mediated gaugino masses, while determined by the infrared spectrum, arise from an explicit sum over UV open string winding modes. We also calculate brane-to-brane tree-level gravity mediated gaugino masses and show that there are two contributions coming from the dilaton and from the twisted modes, which are suppressed by the full T^6 volume and the untwisted T^2 volume respectively.

## Kinetic mixing of U(1)s for local string models

ArXiv (2010)

We study kinetic mixing between massless U(1)s in toroidal orbifolds with D3-branes at orbifold singularities. We focus in particular on C^3/Z_4 singularities but also study C^3/Z_6 and C^3/Z'_6 singularities. We find kinetic mixing can be present and describe the conditions for it to occur. Kinetic mixing comes from winding modes in the N=2 sector of the orbifold. If kinetic mixing is present its size depends only on the complex structure modulus of the torus and is independent of the K\"ahler moduli. We also study gauge threshold corrections for local Z_M x Z_N orbifold models finding that, consistent with previous studies, gauge couplings run from the bulk winding scale rather than the string scale.

## Moduli redefinitions and moduli stabilisation

Journal of High Energy Physics **2010** (2010)

Field redefinitions occur in string compactifications at the one loop level. We review arguments for why such redefinitions occur and study their effect on moduli stabilisation and supersymmetry breaking in the LARGE volume scenario. For small moduli, although the effect of such redefinitions can be larger than that of the α' corrections in both the Kähler and scalar potentials, they do not alter the structure of the scalar potential. For the less well motivated case of large moduli, the redefinitions can dominate all other terms in the scalar potential. We also study the effect of redefinitions on the structure of supersymmetry breaking and soft terms. © SISSA 2010.

## One-loop Yukawa Couplings in Local Models

ArXiv (2010)

We calculate the one-loop Yukawa couplings and threshold corrections for supersymmetric local models of branes at singularities in type IIB string theory. We compute the corrections coming both from wavefunction and vertex renormalisation. The former comes in the IR from conventional field theory running and in the UV from threshold corrections that cause it to run from the winding scale associated to the full Calabi-Yau volume. The vertex correction is naively absent as it appears to correspond to superpotential renormalisation. However, we find that while the Wilsonian superpotential is not renormalised there is a physical vertex correction in the 1PI action associated to light particle loops.

## On Gauge Threshold Corrections for Local IIB/F-theory GUTs

ArXiv (2009)

We study gauge threshold corrections for local GUT models in IIB/F-theory. Consistency with holomorphy requirements of supergravity and the Kaplunovsky-Louis formula implies that the unification scale is enhanced by the bulk radius R from the string scale to M_X =RM_S. We argue that the stringy interpretation of this is via a locally uncancelled tadpole sourced by the hypercharge flux. This sources closed string modes propagating into the bulk; equivalently open string gauge coupling running up to the winding scale M_X. The enhancement to R M_s is tied to GUT breaking by a globally trivial hypercharge flux and will occur in all models realising this mechanism.