751 citations · 2.5k across the 29 of their papers we have counts for
25 papers · 1 filter
Imperfect axions with no domain wall problem
Marco Gorghetto, Edward Hardy, Gilad Perez +1
Post-inflationary axion theories with domain wall number suffer from a domain wall problem. We show analytically, and confirm via simulations, that there is a region of pheno…
Post-inflationary axions: a minimal target for axion haloscopes
Marco Gorghetto, Edward Hardy
An axion-like-particle (ALP) in the post-inflationary scenario with domain wall number can be dark matter if the residual symmetry has a small explicit breakin…
Dark Photon Stars: Formation and Role as Dark Matter Substructure
Marco Gorghetto, Edward Hardy, John March-Russell +2
Any new vector boson with non-zero mass (a `dark photon' or `Proca boson') that is present during inflation is automatically produced at this time from vacuum fluctuations and can…
Axion Quasiparticles for Axion Dark Matter Detection
Jan Schütte-Engel, David J. E. Marsh, Alexander J. Millar +7
It has been suggested that certain antiferromagnetic topological insulators contain axion quasiparticles (AQs), and that such materials could be used to detect axion dark matter (D…
Observing Invisible Axions with Gravitational Waves
Marco Gorghetto, Edward Hardy, Horia Nicolaescu
If the Peccei-Quinn symmetry associated to an axion has ever been restored after inflation, axion strings inevitably produce a contribution to the stochastic gravitational wave bac…
More Axions from Strings
Marco Gorghetto, Edward Hardy, Giovanni Villadoro
We study the contribution to the QCD axion dark matter abundance that is produced by string defects during the so-called scaling regime. Clear evidence of scaling violations is fou…
Hearing without seeing: gravitational waves from hot and cold hidden sectors
Malcolm Fairbairn, Edward Hardy, Alastair Wickens
We study the spectrum of gravitational waves produced by a first order phase transition in a hidden sector that is colder than the visible sector. In this scenario, bubbles of the…
Axions from Strings: the Attractive Solution
Marco Gorghetto, Edward Hardy, Giovanni Villadoro
We study the system of axion strings that forms in the early Universe if the Peccei-Quinn symmetry is restored after inflation. Using numerical simulations, we establish the existe…
Higgs portal dark matter in non-thermal cosmologies
Edward Hardy
A scalar particle with a relic density set by annihilations through a Higgs portal operator is a simple and minimal possibility for dark matter. However, assuming a thermal cosmolo…
Glueball dark matter in non-standard cosmologies
Bobby Samir Acharya, Malcolm Fairbairn, Edward Hardy
Hidden sector glueball dark matter is well motivated by string theory, compactifications of which often have extra gauge groups uncoupled to the visible sector. We study the dynami…
Symmetric and Asymmetric Reheating
Edward Hardy, James Unwin
We study models in which the inflaton is coupled to two otherwise decoupled sectors, and the effect of preheating and related processes on their energy densities during the evoluti…
Stellar cooling bounds on new light particles: plasma mixing effects
Edward Hardy, Robert Lasenby
Strong constraints on the coupling of new light particles to the Standard Model (SM) arise from their production in the hot cores of stars, and the effects of this on stellar cooli…
Miniclusters in the Axiverse
Edward Hardy
If dark matter is an axion-like-particle a significant fraction of the present day relic abundance could be concentrated in compact gravitationally bound miniclusters. We study the…
Dirac vs Majorana gauginos at a 100 TeV collider
Giovanni Grilli di Cortona, Edward Hardy, Andrew J. Powell
We compare the prospects for observing theories with Majorana or Dirac gauginos at a future 100 TeV proton-proton collider. Calculating the expected discovery and exclusion regions…
Diphotons from Diaxions
Luis Aparicio, Aleksandr Azatov, Edward Hardy +1
We study models in which the 750 GeV diphoton excess is due to a scalar decaying to two pseudo-Nambu-Goldstone bosons that subsequently decay into two pairs of highly boosted photo…
The QCD axion, precisely
Giovanni Grilli di Cortona, Edward Hardy, Javier Pardo Vega +1
We show how several properties of the QCD axion can be extracted at high precision using only first principle QCD computations. By combining NLO results obtained in chiral perturba…
Electroweak relaxation from finite temperature
Edward Hardy
We study theories which naturally select a vacuum with parametrically small Electroweak Scale due to finite temperature effects in the early universe. In particular, there is a sca…
Signatures of Large Composite Dark Matter States
Edward Hardy, Robert Lasenby, John March-Russell +1
We investigate the interactions of large composite dark matter (DM) states with the Standard Model (SM) sector. Elastic scattering with SM nuclei can be coherently enhanced by fact…
Big Bang Synthesis of Nuclear Dark Matter
Edward Hardy, Robert Lasenby, John March-Russell +1
We investigate the physics of dark matter models featuring composite bound states carrying a large conserved dark "nucleon" number. The properties of sufficiently large dark nuclei…
Annihilation Signals from Asymmetric Dark Matter
Edward Hardy, Robert Lasenby, James Unwin
In the simplest models of asymmetric dark matter (ADM) annihilation signals are not expected, since the DM is non-self-conjugate and the relic density of anti-DM is negligible. We…
Heavy superpartners with less tuning from hidden sector renormalisation
Edward Hardy
In supersymmetric extensions of the Standard Model, superpartner masses consistent with collider bounds typically introduce significant tuning of the electroweak scale. We show tha…
Is Natural SUSY Natural?
Edward Hardy
We study the fine tuning associated to a `Natural Supersymmetry' spectrum with stops, after RG running, significantly lighter than the first two generation sfermions and the gluino…
Retrofitted Natural Supersymmetry from a U(1)
Edward Hardy, John March-Russell
We propose that a single, spontaneously broken, U(1) gauge symmetry may be responsible for suppressing both the first two generation Yukawa couplings, and also, in a correlated man…
Axion Mediation
Masha Baryakhtar, Edward Hardy, John March-Russell
We explore the possibility that supersymmetry breaking is mediated to the Standard Model sector through the interactions of a generalized axion multiplet that gains a F-term expect…