Conveners
Parallel sessions: Cosmology (ACGRG/NZ Gravity Student Talks)
- Krzysztof Bolejko
Parallel sessions: Gravitational waves (ACGRG/NZ Gravity Student Talks)
- Richard Easther
Parallel sessions: Black holes - Mathematical aspects
- Bin Wang (SJTU/YZU)
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Joshua Ritchie (University of Otago)06/07/2026, 13:30Parallel Session Talk
We investigate the asymptotic behaviour of solutions to the Euler equations on fixed Kasner-type backgrounds. In particular, we focus on backgrounds with a non-constant multiplicity and non-constant fluid-type. i.e., backgrounds for which the Kasner exponents and the speed-of-sound-squared do not have a fixed ordering over the spatial manifold. The primary focus here is on developing an...
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GEONWOO KANG (Seoul National University)06/07/2026, 13:50Parallel Session Talk
We present a powerful new diagnostics by which the running of scalar spectral index of primordial density fluctuations can be tightly and independently constrained. This new diagnostics utilizes coherent rotation of void galaxies, which can be observed as redshift asymmetry in opposite sides dichotomized by the projected spin axes of hosting voids. Comparing the numerical results from the...
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Gawain Simpson (University of Tasmania)06/07/2026, 14:10Parallel Session Talk
Dark energy drives the present accelerated expansion of the universe, yet its
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physical nature remains uncertain. Its properties are characterised by the equation of state w = p/ρ, with w = −1 corresponding to a cosmological constant.
Determining whether w deviates from this value is crucial, since w < −1 would
imply a future Big Rip singularity in homogeneous cosmological models.
I present... -
Che Li (The Chinese University of Hong Kong)06/07/2026, 14:30Parallel Session Talk
The cosmological principle postulates that our universe is homogeneous and isotropic. Based on such assumptions, the LCDM model is proposed with its underlying FLRW metric. The structure formation in the late time universe breaks the assumption of homogeneity. From the perspective of general relativity, inhomogeneous matter distribution should also be coupled with an inhomogeneous background...
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Morag Hills (University of Canterbury)06/07/2026, 14:50Parallel Session Talk
Inhomogeneous cosmological models, such as the $\Lambda$-Szekeres model, provide a fully general relativistic way of describing structures in the local Universe through exact solutions of Einstein's equations. They thus provide a natural test bed to gauge the impact of local structures on cosmological inferences. We present the results of two separate but related investigations in which we...
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SHANGJIE JIN (University of Western Australia)08/07/2026, 13:30Parallel Session Talk
In recent years, with the improvements of the measurement precisions of cosmological parameters, some puzzling tensions appear. The tension between the values of the Hubble constant inferred from the Planck CMB observations (0.8% precision, assuming the standard LambdaCDM model) and obtained through distance ladder measurements have reached 5σ, known as the Hubble tension. Gravitational wave...
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Laura Burn (University of Auckland)08/07/2026, 13:50Parallel Session Talk
Primordial black holes (PBHs), assumed to form in the early Universe, remain a viable dark matter candidate. Since dark matter is expected to be concentrated toward galactic centres, a significant population of PBHs would reside near a supermassive black hole (SMBH), creating a promising environment for gravitational wave emission. We consider a population of PBHs with masses in the range...
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Tarin Eccleston (The University of Auckland)08/07/2026, 14:10Parallel Session Talk
There have only been a few recorded observations of supernovae in the Milky Way. The earliest was seen by Han-dynasty astronomers in 185 CE, while the most recent is thought to be in the late 1600s. Supernovae have appeared as unexpected guests in the sky throughout history, and we have not yet observed them in detail. But well before the star dies, it releases invisible messengers –...
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Russell Boey (University of Auckland)08/07/2026, 14:30Parallel Session Talk
Ultralight dark matter (ULDM) is a dark matter candidate composed of light axion-like particles and is a promising alternative to cold dark matter. A feature unique to ULDM is the formation of soliton cores at the centre of galaxies, whose interactions with supermassive black holes may affect their merger dynamics. We present high-resolution numerical simulations of merging binary solitons...
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Jesse Satherley (University of Canterbury)08/07/2026, 14:50Parallel Session Talk
The interaction between GWs and EWs is interesting, but it has only been explored in the vacuum case.
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Theory for the non-vacuum case does exist, but it has not been implemented numerically.
We extend current initial value boundary problem numerical simulations to include an arbitrary energy-momentum tensor, which is then used to prescribe electromagnetism.
However, adding electromagnetism... -
Arthur Suvorov (University of Alicante)09/07/2026, 13:30Parallel Session Talk
As proven by Simon, Beig, and others from the 1960s on, Einstein spacetimes are uniquely decomposable into a set of multipole moments. The Geroch-Hansen or Thorne moments are often used to categorise radiation patterns, tidal deformations, geodesics, and other phenomena associated with compact objects, and these theorems ensure such descriptions are complete in some sense. What if we drop the...
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Dr De-Chang Dai (National Dong Hwa University)09/07/2026, 13:50Parallel Session Talk
We study the retrograde second caustics of extremal Kerr black holes, where the intensity of the light beam is infinitely magnified. We find that the caustics of different polarized beams are split by as much as 10−3 rad by an external black hole for a suitable range of parameters. A lensing black hole at several lys away separates the polarized beams about 1012 m apart. This splitting is...
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Finnian Gray (Macquarie University)09/07/2026, 14:10Parallel Session Talk
I will discuss a recently proposed class of Generalized Lense–Thirring spacetimes in all dimensions. The class represent an ansatz for slowly rotating black holes which can be applied to solve the equations of motion, to linear order in the rotation parameters, for a wide variety of gravitational theories including Einstein--Gravity. In this case it is equivalent to the original Lense--Thiring...
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Yehui Hou (Tsung-Dao Lee Institute)09/07/2026, 14:30Parallel Session Talk
A key challenge in imaging supermassive black holes is disentangling gravitational effects from plasma physics in order to accurately determine spacetime properties, particularly black hole spin. In this Letter, we present a fully covariant and rigorous analysis of the synchrotron emission from accreting plasma in the equatorial plane in the stationary, axisymmetric, high-conductivity regime...
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Matt Visser (Victoria University of Wellington)09/07/2026, 14:50Parallel Session Talk
The event horizons, and Cauchy horizons, of mathematical General Relativity are mathematical idealisations that are not particularly well suited to questions that physicists and astronomers like to ask.
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For very many purposes dynamical trapping horizons are much more suitable. I shall give a brief overview of the current situation.