# Publications by Joseph Conlon

## Searches for 3.5 keV Absorption Features in Cluster AGN Spectra

Monthly Notices of the Royal Astronomical Society Blackwell Publishing Inc. (0)

We investigate possible evidence for a spectral dip around 3.5 keV in central cluster AGNs, motivated by previous results for archival Chandra observations of the Perseus cluster and the general interest in novel spectral features around 3.5 keV that may arise from dark matter physics. We use two deep Chandra observations of the Perseus and Virgo clusters that have recently been made public. In both cases, mild improvements in the fit ($\Delta \chi^2 = 4.2$ and $\Delta \chi^2 = 2.5$) are found by including such a dip at 3.5 keV into the spectrum. A comparable result ($\Delta \chi^2 = 6.5$) is found re-analysing archival on-axis Chandra ACIS-S observations of the centre of the Perseus cluster.

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

ArXiv (0)

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.

## Brane-Antibrane Backreaction in Axion Monodromy Inflation

ArXiv (0)

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.

## Quantum Gravity Constraints on Inflation

ArXiv (0)

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.

## Aspects of Flavour and Supersymmetry in F-theory GUTs

ArXiv (0)

We study the constraints of supersymmetry on flavour in recently proposed models of F-theory GUTs. We relate the topologically twisted theory to the canonical presentation of eight-dimensional super Yang-Mills and provide a dictionary between the two. We describe the constraints on Yukawa couplings implied by holomorphy of the superpotential in the effective 4-dimensional supergravity theory, including the scaling with \alpha_{GUT}. Taking D-terms into account we solve explicitly to second order for wavefunctions and Yukawas due to metric and flux perturbations and find a rank-one Yukawa matrix with no subleading corrections.

## One-loop Yukawa Couplings in Local Models

ArXiv (0)

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.

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

ArXiv (0)

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.

## Gauge Threshold Corrections for Local String Models

ArXiv (0)

We study gauge threshold corrections for local brane models embedded in a large compact space. A large bulk volume gives important contributions to the Konishi and super-Weyl anomalies and the effective field theory analysis implies the unification scale should be enhanced in a model-independent way from M_s to R M_s. For local D3/D3 models this result is supported by the explicit string computations. In this case the scale R M_s comes from the necessity of global cancellation of RR tadpoles sourced by the local model. We also study D3/D7 models and discuss discrepancies with the effective field theory analysis. We comment on phenomenological implications for gauge coupling unification and for the GUT scale.

## SUSY Breaking in Local String/F-Theory Models

ArXiv (0)

We investigate bulk moduli stabilisation and supersymmetry breaking in local string/F-theory models where the Standard Model is supported on a del Pezzo surface or singularity. Computing the gravity mediated soft terms on the Standard Model brane induced by bulk supersymmetry breaking in the LARGE volume scenario, we explicitly find suppressions by M_s/M_P ~ V^{-1/2} compared to M_{3/2}. This gives rise to several phenomenological scenarios, depending on the strength of perturbative corrections to the effective action and the source of de Sitter lifting, in which the soft terms are suppressed by at least M_P/V^{3/2} and may be as small as M_P/V^2. Since the gravitino mass is of order M_{3/2} ~ M_P/V, for TeV soft terms all these scenarios give a very heavy gravitino (M_{3/2} >= 10^8 GeV) and generically the lightest moduli field is also heavy enough (m >= 10 TeV) to avoid the cosmological moduli problem. For TeV soft terms, these scenarios predict a minimal value of the volume to be V ~ 10^{6-7} in string units, which would give a unification scale of order M_{GUT} ~ M_s V^{1/6} ~ 10^{16} GeV. The strong suppression of gravity mediated soft terms could also possibly allow a scenario of dominant gauge mediation in the visible sector but with a very heavy gravitino M_{3/2} > 1 TeV.

## General Analysis of LARGE Volume Scenarios with String Loop Moduli Stabilisation

ArXiv (0)

We study the topological conditions for general Calabi-Yaus to get a non-supersymmetric AdS exponentially large volume minimum of the scalar potential in flux compactifications of IIB string theory. We show that negative Euler number and the existence of at least one blow-up mode resolving point-like singularities are necessary and sufficient conditions for moduli stabilisation with exponentially large volumes. We also analyse the general effects of string loop corrections on this scenario. While the combination of alpha' and nonperturbative corrections are sufficient to stabilise blow-up modes and the overall volume, quantum corrections are needed to stabilise other directions transverse to the overall volume. This allows exponentially large volume minima to be realised for fibration Calabi-Yaus, with the various moduli of the fibration all being stabilised at exponentially large values. String loop corrections may also play a role in stabilising 4-cycles which support chiral matter and cannot enter directly into the non-perturbative superpotential. We illustrate these ideas by studying the scalar potential for various Calabi-Yau three-folds including K3 fibrations and briefly discuss the potential phenomenological and cosmological implications of our results.

## Systematics of String Loop Corrections in Type IIB Calabi-Yau Flux Compactifications

ArXiv (0)

We study the behaviour of the string loop corrections to the N=1 4D supergravity Kaehler potential that occur in flux compactifications of IIB string theory on general Calabi-Yau three-folds. We give a low energy interpretation for the conjecture of Berg, Haack and Pajer for the form of the loop corrections to the Kaehler potential. We check the consistency of this interpretation in several examples. We show that for arbitrary Calabi-Yaus, the leading contribution of these corrections to the scalar potential is always vanishing, giving an "extended no-scale structure". This result holds as long as the corrections are homogeneous functions of degree -2 in the 2-cycle volumes. We use the Coleman-Weinberg potential to motivate this cancellation from the viewpoint of low-energy field theory. Finally we give a simple formula for the 1-loop correction to the scalar potential in terms of the tree-level Kaehler metric and the correction to the Kaehler potential. We illustrate our ideas with several examples. A companion paper will use these results in the study of Kaehler moduli stabilisation.

## Wave Functions and Yukawa Couplings in Local String Compactifications

ArXiv (0)

We consider local models of magnetised D7 branes in IIB string compactifications, focussing on cases where an explicit metric can be written for the local 4-cycle. The presence of an explicit metric allows analytic expressions for the gauge bundle and for the chiral matter wavefunctions through solving the Dirac and Laplace equations. The triple overlap of the normalised matter wavefunctions generates the physical Yukawa couplings. Our main examples are the cases of D7 branes on P1xP1 and P2. We consider both supersymmetric and non-supersymmetric gauge backgrounds and both Abelian and non-Abelian gauge bundles. We briefly outline potential phenomenological applications of our results.

## Mirror Mediation

ArXiv (0)

I show that the effective action of string compactifications has a structure that can naturally solve the supersymmetric flavour and CP problems. At leading order in the g_s and \alpha' expansions, the hidden sector factorises. The moduli space splits into two mirror parts that depend on Kahler and complex structure moduli. Holomorphy implies the flavour structure of the Yukawa couplings arises in only one part. In type IIA string theory flavour arises through the Kahler moduli sector and in type IIB flavour arises through the complex structure moduli sector. This factorisation gives a simple solution to the supersymmetric flavour and CP problems: flavour physics is generated in one sector while supersymmetry is broken in the mirror sector. This mechanism does not require the presence of gauge, gaugino or anomaly mediation and is explicitly realised by phenomenological models of IIB flux compactifications.

## Astrophysical and Cosmological Implications of Large Volume String Compactifications

ArXiv (0)

We study the spectrum, couplings and cosmological and astrophysical implications of the moduli fields for the class of Calabi-Yau IIB string compactifications for which moduli stabilisation leads to an exponentially large volume V ~ 10^{15} l_s^6 and an intermediate string scale m_s ~ 10^{11}GeV, with TeV-scale observable supersymmetry breaking. All K\"ahler moduli except for the overall volume are heavier than the susy breaking scale, with m ~ ln(M_P/m_{3/2}) m_{3/2} ~ (\ln(M_P/m_{3/2}))^2 m_{susy} ~ 500 TeV and, contrary to standard expectations, have matter couplings suppressed only by the string scale rather than the Planck scale. These decay to matter early in the history of the universe, with a reheat temperature T ~ 10^7 GeV, and are free from the cosmological moduli problem (CMP). The heavy moduli have a branching ratio to gravitino pairs of 10^{-30} and do not suffer from the gravitino overproduction problem. The overall volume modulus is a distinctive feature of these models and is an M_{planck}-coupled scalar of mass m ~ 1 MeV and subject to the CMP. A period of thermal inflation can help relax this problem. This field has a lifetime ~ 10^{24}s and can contribute to dark matter. It may be detected through its decays to 2\gamma or e^+e^-. If accessible the e^+e^- decay mode dominates, with Br(\chi \to 2 \gamma) suppressed by a factor (ln(M_P/m_{3/2}))^2. We consider the potential for detection of this field through different astrophysical sources and find that the observed gamma-ray background constrains \Omega_{\chi} <~ 10^{-4}. The decays of this field may generate the 511 keV emission line from the galactic centre observed by INTEGRAL/SPI.

## Scanning the Landscape of Flux Compactifications: Vacuum Structure and Soft Supersymmetry Breaking

ArXiv (0)

We scan the landscape of flux compactifications for the Calabi-Yau manifold $\mathbb{P}^4_{[1,1,1,6,9]}$ with two K\" ahler moduli by varying the value of the flux superpotential $W_0$ over a large range of values. We do not include uplift terms. We find a rich phase structure of AdS and dS vacua. Starting with $W_0\sim 1$ we reproduce the exponentially large volume scenario, but as $W_0$ is reduced new classes of minima appear. One of them corresponds to the supersymmetric KKLT vacuum while the other is a new, deeper non-supersymmetric minimum. We study how the bare cosmological constant and the soft supersymmetry breaking parameters for matter on D7 branes depend on $W_0$, for these classes of minima. We discuss potential applications of our results.

## The QCD Axion and Moduli Stabilisation

ArXiv (0)

We investigate the conditions for a QCD axion to coexist with stabilised moduli in string compactifications. We show how the simplest approaches to moduli stabilisation give unacceptably large masses to the axions. We observe that solving the F-term equations is insufficient for realistic moduli stabilisation and give a no-go theorem on supersymmetric moduli stabilisation with unfixed axions applicable to all string compactifications and relevant to much current work. We demonstrate how nonsupersymmetric moduli stabilisation with unfixed axions can be realised. We finally outline how to stabilise the moduli such that f_a is within the allowed window 10^9 GeV < f_a < 10^{12} GeV, with f_a ~ \sqrt{M_{SUSY} M_P}.

## Type IIA Orientifolds on General Supersymmetric Z_N Orbifolds

ArXiv (0)

We construct Type IIA orientifolds for general supersymmetric Z_N orbifolds. In particular, we provide the methods to deal with the non-factorisable six-dimensional tori for the cases Z7, Z8, Z8', Z12 and Z12'. As an application of these methods we explicitly construct many new orientifold models.

## Field Identifications for Interacting Bosonic Models in N=2 Superconformal Field Theory

ArXiv (0)

We study a family of interacting bosonic representations of the N=2 superconformal algebra. These models can be tensored with a conjugate theory to give the free theory. We explain how to use free fields to study interacting fields and their dimensions, and how we may identify different free fields as representing the same interacting field. We show how a lattice of identifying fields may be built up and how every free field may be reduced to a standard form, thus permitting the resolution of the spectrum. We explain how to build the extended algebra and show that there are a finite number of primary fields for this algebra for any of the models. We illustrate this by studying an example.

## A Note on Brane Inflation

ArXiv (0)

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.

## Gaugino and Scalar Masses in the Landscape

ArXiv (0)

In this letter we demonstrate the genericity of suppressed gaugino masses M_a \sim m_{3/2}/ln(M_P/m_{3/2}) in the IIB string landscape, by showing that this relation holds for D7-brane gauginos whenever the associated modulus is stabilised by nonperturbative effects. Although m_{3/2} and M_a take many different values across the landscape, the above small mass hierarchy is maintained. We show that it is valid for models with an arbitrary number of moduli and applies to both the KKLT and exponentially large volume approaches to Kahler moduli stabilisation. In the latter case we explicitly calculate gaugino and moduli masses for compactifications on the two-modulus Calabi-Yau P^4_[1,1,1,6,9]. In the large-volume scenario we also show that soft scalar masses are approximately universal with m_i^2 \sim m_{3/2}^2 (1 + \epsilon_i), with the non-universality parametrised by \epsilon_i \sim 1/ln (M_P/m_{3/2})^2 \sim 1/1000. We briefly discuss possible phenomenological implications of our results.