4 research outputs found
A thorough investigation of the prospects of eLISA in addressing the Hubble tension: Fisher Forecast, MCMC and Machine Learning
We carry out an in-depth analysis of the capability of the upcoming
space-based gravitational wave mission eLISA in addressing the Hubble tension,
with a primary focus on observations at intermediate redshifts (). We
consider six different parametrizations representing different classes of
cosmological models, which we constrain using the latest datasets of cosmic
microwave background (CMB), baryon acoustic oscillations (BAO), and type Ia
supernovae (SNIa) observations, in order to find out the up-to-date tensions
with direct measurement data. Subsequently, these constraints are used as
fiducials to construct mock catalogs for eLISA. We then employ Fisher analysis
to forecast the future performance of each model in the context of eLISA. We
further implement traditional Markov Chain Monte Carlo (MCMC) to estimate the
parameters from the simulated catalogs. Finally, we utilize Gaussian Processes
(GP), a machine learning algorithm, for reconstructing the Hubble parameter
directly from simulated data. Based on our analysis, we present a thorough
comparison of the three methods as forecasting tools. Our Fisher analysis
confirms that eLISA would constrain the Hubble constant () at the
sub-percent level. MCMC/GP results predict reduced tensions for
models/fiducials which are currently harder to reconcile with direct
measurements of , whereas no significant change occurs for
models/fiducials at lesser tensions with the latter. This feature warrants
further investigation in this direction.Comment: To appear in JCAP, 30 pages, 12 sets of figures, 7 table
Reconstructing the Hubble parameter with future Gravitational Wave missions using Machine Learning
We study the prospects of Machine Learning algorithms like Gaussian processes
(GP) as a tool to reconstruct the Hubble parameter with two upcoming
gravitational wave missions, namely the evolved Laser Interferometer Space
Antenna (eLISA) and the Einstein Telescope (ET). We perform non-parametric
reconstructions of with GP using realistically generated catalogues,
assuming various background cosmological models, for each mission. We also take
into account the effect of early-time and late-time priors separately on the
reconstruction, and hence on the Hubble constant (). Our analysis reveals
that GPs are quite robust in reconstructing the expansion history of the
Universe within the observational window of the specific mission under study.
We further confirm that both eLISA and ET would be able to constrain and
to a much higher precision than possible today, and also find out their
possible role in addressing the Hubble tension for each model, on a
case-by-case basis.Comment: 9 pages, 5 sets of figure
Moduli stabilization with bulk scalar in nested doubly warped braneworld model
We examine the modulus stabilization mechanism of a warped geometry model with nested warping. Such a model with multiple moduli is known to offer a possible resolution of the fermion mass hierarchy problem in the Standard Model. A six dimensional doubly warped braneworld model under consideration admits two distinct moduli, with the associated warp factors dynamically generating different physical mass scales on four 3-branes. In order to address the hierarchy problem related to the Higgs mass, both moduli need to be stabilized around their desired values without any extreme fine tuning of parameters. We show that it is possible to stabilize them simultaneously due to the appearence of an effective 4D moduli potential, which is generated by a single massive bulk scalar field having non-zero VEVs frozen on the 3-branes. This gives rise to two scalar radions, one of which has mass slightly below (TeV) and couplings to SM fields proportional to the inverse of its (TeV) VEV, and the other has nearly mass and interactions with SM fields suppressed by the Planck scale. We also discuss how the entire mechanism can possibly be understood from a purely gravitational point of view, with higher curvature f(R) contributions in the bulk automatically providing a scalar degree of freedom that can serve as the stabilizing field in the Einstein frame
Nested warped geometry in a non-flat braneworld scenario
Abstract We generalize nested multiply warped braneworld models by incorporating non-zero brane curvature caused by an effective cosmological constant Ω induced on the 3-branes. Starting with the doubly warped model, we first analyze the case where the maximally warped brane is identified as the visible brane. For Ω > 0 , the latter is not possible but the tuning of the cosmological constant to its tiny observed value is linked to the tuning of the extra dimensional moduli close to the inverse Planck length, justifying the original flat brane approximation. In both regimes, we study the dependence of the scale-clustering of the pair of TeV-branes on the brane cosmological constant and hence its potential role in generating a fermion mass hierarchy between these branes. Identifying the near-maximally warped brane as the visible brane instead opens up regions in the parameter space that allow positive 3-brane tensions for both anti de Sitter and de Sitter branes, subject to non-trivial constraints on the warping parameters. We conclude by generalizing the key results to arbitrary n-fold nested warped braneworlds