A5082539918- Cosmology and Gravitation Theories
- Black Holes and Theoretical Physics
- Galaxies: Formation, Evolution, Phenomena
- Solar and Space Plasma Dynamics
- Geophysics and Gravity Measurements
- Dark Matter and Cosmic Phenomena
- Pulsars and Gravitational Waves Research
- Astronomy and Astrophysical Research
- Scientific Research and Discoveries
- Advanced Differential Geometry Research
- Relativity and Gravitational Theory
- Stochastic processes and financial applications
- Theoretical and Computational Physics
- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Advanced Thermodynamics and Statistical Mechanics
- Stochastic processes and statistical mechanics
- Computational Physics and Python Applications
- Radio Astronomy Observations and Technology
- Cybercrime and Law Enforcement Studies
- Flow Measurement and Analysis
- Neutrino Physics Research
- Quantum Mechanics and Applications
- Geometric Analysis and Curvature Flows
- Acoustic Wave Phenomena Research
University of Sussex
2015-2024
University of North Carolina at Chapel Hill
2021
European Organization for Nuclear Research
2012-2013
Netherlands Institute for Radio Astronomy
2013
Bielefeld University
2010-2012
Heidelberg University
2008-2010
Heidelberg Institute for Theoretical Studies
2009
University of Portsmouth
2006-2007
University of Newcastle Australia
1984
We derive analytic bounds on the shape of primordial power spectrum in context single-field inflation. In particular, steepest possible growth has a spectral index $n_s - 1 = 4$ once transients have died down. Its primary implication is that any constraint at particular scale can be extrapolated to an upper bound over extended range scales. This important for models which generate relics due enhanced amplitude scalar perturbations, such as black holes. order them, needs grow many orders...
The grand challenges of contemporary fundamental physics---dark matter, dark energy, vacuum inflation and early universe cosmology, singularities the hierarchy problem---all involve gravity as a key component. And all gravitational phenomena, black holes stand out in their elegant simplicity, while harbouring some most remarkable predictions General Relativity: event horizons, ergoregions. hitherto invisible landscape Universe is being unveiled before our eyes: historical direct detection...
We reinspect the calculation for mass fraction of primordial black holes (PBHs) which are formed from perturbations, finding that performing using comoving curvature perturbation $\mathcal{R}_{c}$ in standard way vastly overestimates number PBHs, by many orders magnitude. This is because PBHs form shortly after horizon entry, meaning modes significantly larger than PBH unobservable and should not affect whether a forms or - this important effect taken into account smoothing distribution...
The formation and abundance of primordial black holes (PBHs) arising from the curvature perturbation ζ is studied. non-linear relation between density contrast δ means that, even when has an exactly Gaussian distribution, significant non-Gaussianities affecting PBH must be considered. Numerical simulations are used to investigate critical value mass PBHs which form, peaks theory calculate fraction universe collapsing form at time formation. A formalism total present day function also...
We compare primordial black hole (PBH) constraints on the power spectrum and mass distributions using traditional Press Schechter formalism, peaks theory, a recently developed version of theory relevant to PBHs. show that, provided PBH formation criteria smoothing are treated consistently, only vary by ∼ 10% between methods (a difference that will become increasingly important with better data). Our robust from PBHs take into account effects critical collapse, non-linear relation ζ δ, shift...
Abstract Phase transitions in the early universe lead to a reduction equation of state primordial plasma. This exponentially enhances formation rate black holes. However, this sensitivity is same that hole abundances show curvature power spectrum amplitude. In paper, we investigate peaked spectra and challenges associated with motivating populations holes standard model enhancements. The parametrisation different plays an important role discussion. allowed parameter space consistent large...
We use the $\ensuremath{\delta}N$ formalism to describe leading order contributions primordial power spectrum, bispectrum, and trispectrum in multiple-field models of inflation at a perturbative expansion. In slow-roll where initial field fluctuations Hubble exit are nearly Gaussian, any detectable non-Gaussianity is expected come from super-Hubble evolution. show that contribution can be described by two nonlinearity parameters, ${\ensuremath{\tau}}_{NL}$ ${g}_{NL}$, which dependent upon...
Primordial Black Holes (PBH's) can form in the early Universe from collapse of large density fluctuations. Tight observational limits on their abundance constrain amplitude primordial fluctuations very small scales which not otherwise be constrained, with PBH's only forming extremely rare The number formed is therefore sensitive to changes shape tail fluctuation distribution, itself depends amount non-Gaussianity present. We study, for first time, how quadratic and cubic local arbitrary size...
We review models which generate a large non-Gaussianity of the local form. first briefly consider three either at or after end inflation; curvaton scenario, modulated (p)reheating and an inhomogeneous inflation. then focus on ways generating during derive general conditions product sum separable potential must satisfy in order to bispectrum slow-roll As application we two-field hybrid formalism not based slow roll can be applied parameters become before inflation ends. An exactly soluble...
We conduct a thorough Bayesian analysis of the possibility that black hole merger events seen in gravitational waves are primordial (PBH) mergers. Using latest rate models for PBH binaries drawn from lognormal mass function we compute posterior parameter constraints and evidences using data first two observing runs LIGO-Virgo. account theoretical uncertainty due to possible disruption binary by surrounding PBHs, which can suppress significantly. also consider simple astrophysically motivated...
We recently showed that postulated ultracompact minihalos with a steep density profile do not form in realistic simulations enhanced initial perturbations. In this paper we assume small fraction of the dark matter consists primordial black holes (PBHs) and simulate formation structures around them. find scenario halos profiles form, consistent theoretical predictions. If rest weakly interacting massive particles (WIMPs), also show WIMPs dense innermost part these would annihilate produce...
We have calculated the detectable merger rate of primordial black holes, as a function redshift, well binary's mass ratio, total and chirp (observables that not previously been explored in great detail for PBHs). consider both current design sensitivity LIGO five different hole functions, showing comparison to predicted astrophysical rate. show empirical preference nearly equal-mass binaries LIGO/Virgo data can be consistent with PBH hypothesis once observational selection effects are taken...
All single-field inflationary models invoke varying degrees of tuning in order to account for cosmological observations. Mechanisms that generate primordial black holes (PBHs) from enhancement power at small scales posit potentials transiently break scale invariance and possibly adiabaticity over a range modes. This requires additional on top required observations probed by cosmic microwave background (CMB) anisotropies. In this paper we study the parametric dependence various inflation...
We calculate the power spectra of primordial curvature and isocurvature perturbations from a general two-field inflation model at next-to-leading order correction in slow-roll expansion. In particular we spectral indices to second parameters. show that cross correlation time Hubble exit during is nonzero first apply our results different classes inflation, including inflaton curvaton scenarios. The spectrum gravitational waves, obey generalized consistency relations models. give two an...
We study the level of primordial non-Gaussianity in slow-roll two-field inflation. Using an analytic formula for non-linear parameter fNL case a sum or product separable potential, we find that it is possible to generate significant even during inflation with Gaussian perturbations at Hubble exit. In this paper give general conditions obtaining large and calculate fine-tuning required obtain this. present explicit models which end can exceed current observational bound .
A new and powerful probe of the origin evolution structures in Universe has emerged been actively developed over last decade. In coming decade, non-Gaussianity, i.e., study non-Gaussian contributions to correlations cosmological fluctuations, will become an important both early late Universe. Specifically, it play a leading role furthering our understanding two fundamental aspects cosmology astrophysics: (i) physics very universe that created primordial seeds for large-scale structures, (ii)...
We consider possible scale-dependence of the non-linearity parameter fNL in local and quasi-local models non-Gaussian primordial density perturbations. In simplest model where perturbations are a quadratic function single Gaussian field then is scale-independent by construction. However can arise due to either more than one field, or non-linear evolution modes after horizon-exit during inflation. show that scale dependence typically first order slow-roll. For some this may be observable with...
We outline the expected constraints on non-Gaussianity from cosmic microwave background (CMB) with current and future experiments, focusing both third (f_{NL}) fourth-order (g_{NL} \tau_{NL}) amplitudes of local configuration or non-Gaussianity. The experimental focus is skewness (two-to-one) kurtosis (two-to-two three-to-one) power spectra weighted maps. In adition to a measurement \tau_{NL} g_{NL} WMAP 5-year data, our study provides first forecasts for g_{NL}. describe how these...
We study the generation of non-Gaussianity in models hybrid inflation with two inflaton fields, (2-brid inflation). analyse region parameter and initial condition space where a large may be generated during slow-roll which is generally characterised by fNL, τNL small gNL. For certain values we can satisfy >> fNL2. The bispectrum local type but have significant scale dependence. show that loop corrections to power spectrum are suppressed inflation, if one assume fields follow classical...
We study the non-Gaussianity generated during multiple-field inflation. provide an exact expression for bispectrum parameter f_NL which is valid beyond slow-roll regime, certain classes of inflationary models. then a new, multi-field model considering case where grows to observable values at end show that in this trispectrum also large and may even dominant signal non-Gaussianity.
Primordial black holes (PBHs) can form in the early Universe from collapse of rare, large density fluctuations. They have never been observed, but this fact is enough to constrain amplitude fluctuations on very small scales which cannot be otherwise probed. Because PBHs only rare fluctuations, number formed extremely sensitive changes shape tail fluctuation distribution - depends amount non-Gaussianity present. We first study how local arbitrary size up fifth order affects abundance and...
Making use of definitive new lattice computations the Standard Model thermodynamics during quantum chromodynamic (QCD) phase transition, we calculate enhancement in mass distribution primordial black holes (PBHs) due to softening equation state. We find that peaks at approximately $0.7M_\odot$, with formation rate increasing by least two orders magnitude state this time, a range $0.3M_\odot<M<1.4M_\odot$ full width half-maximum. PBH is increased smaller amount for PBHs masses spanning large...
If the primordial curvature perturbation followed a Gaussian distribution, black holes (PBHs) will be Poisson distributed with no additional clustering. We consider local non-Gaussianity and its impact on initial PBH clustering mass function due to mode coupling between long short wavelength modes. show that even small amount of results in significant enhancement subsequent merger rate shifts higher PBHs. However, as becomes strong, number density PBHs large, leading large theoretical...
Our current understanding of the Universe is established through pristine measurements structure in cosmic microwave background (CMB) and distribution shapes galaxies tracing large scale (LSS) Universe. One key ingredient that underlies cosmological observables field sources observed assumed to be initially Gaussian with high precision. Nevertheless, a minimal deviation from Gaussianityis perhaps most robust theoretical prediction models explain Universe; itis necessarily present even...