How does the speedup trick affect the performance of the algorithm?

With simulations of the nDGP model, Barreira, Bose, and Li (2015) demonstrated that it is possible to speed up the performance of the algorithm by a factor of 10, with little loss in accuracy in the matter power spectrum for k ≲ 5 h=Mpc; halo properties such as their abundance, mass, density profiles, and peculiar velocity were also virtually unaffected by the speedup trick.

What is the main reason for the voids to become more efficient?

if the growth of structure is boosted, then voids become emptier as the mass outflows toward their surrounding walls and filaments become more efficient (Cai, Padilla, and Li, 2015; Zivick et al., 2015).

What is the first challenge facing the utility of voids as a cosmological probe?

In practice, a first challenge facing the utility of voids as a cosmological probe lies in how to identify them from the complicated cosmic web.

How do you get the leading-order correction to the linear power spectrum?

To obtain the leading-order correction to the linear power spectrum, the one-loop power spectrum, solutions for these quantities need to be obtained up to the third order in perturbations.

What are the common types of redshift fitting codes?

Photometric redshift fitting codes usually rely on representative spectroscopic training samples, which allow the measured redshifts to reach accuracies of Δz=z≳Oð10−2Þ.

What is the way to improve the performance of the DGP simu-lations?

Another way to improve the performance of these simu-lations is to first manipulate the target equations (in particular, those involving nonlinear terms of the partial derivatives of ϕ) analytically and try to recast them into a more numerically stable form.

What is the way to enforce a near cancellation of a gravity theory?

Without some physical principle or symmetry to enforce such a near cancellation, this would seem to require a significant degree of fine-tuning of the theory.

What are the advantages of distance indicators for chameleons?

Distance indicators are invaluable for testing chameleon theories since they are both sensitive to gravity and can be observed in void dwarf galaxies that are least likely to be screened.

What is the minimum mass for which the star can burn hydrogen?

The latter is the minimum mass for which the star can burn hydrogen continuously and stably; i.e., the energy from hydrogen burning in the core is balanced by losses at the surface.

What are the parameters used to constrain the deviations of gravity in the linear regime?

—As detailed in Sec. VIII, large-scale measurements of lensing, redshiftspace distortions, and other observables have been used to constrain parameters for the deviations of gravity in the linear regime.

What is the way to rule out the finely tuned models of this kind?

The most finely tuned models of this kind can be ruled out by a second set of BNS merger observations at a higher redshift than GW170817.

Open AccessJournal Article10.1103/REVMODPHYS.93.015003

Novel Probes Project: Tests of gravity on astrophysical scales

Tessa Baker, +10 more

- 10 Feb 2021

- Reviews of Modern Physics

- Vol. 93, Iss: 1, pp 015003

106

TL;DR: In this article, a survey of the constraints on modified-gravity models using astrophysical objects in the cosmological, weak-field regime is presented, embedded in the framework of the novel probes project, a forum connecting observers and theorists involved in the study of dark sector interactions.

Abstract: Modern instruments and observational programs in astrophysics and cosmology have opened new perspectives for probing general relativity on previously unexplored scales. This review provides both a methodological and an observational survey of the constraints on modified-gravity models using astrophysical objects in the cosmological, weak-field regime. It is embedded in the framework of the novel probes project, a forum connecting observers and theorists involved in the study of astrophysical tests of dark sector interactions.

1. What contributions have the authors mentioned in the paper "Novel probes project: tests of gravity on astrophysical scales" ?

( published 10 February 2021 ) The Novel Probes Project, an initiative to advance the field of astrophysical tests of the dark sector by creating a forum that connects observers and theorists, is introduced.. This review focuses on tests of gravity and is intended to be of use primarily to observers, as well as theorists with an interest in the development of experimental tests.

2. What can be done to slow down the decay of the gravitational potential?

For instance, a stronger gravity can work to slow down the decay of the gravitational potential (or even make it grow), thereby leading to a weaker amplitude of the cold spots (or turning them into hot spots).

3. What is the effect of a face-on infall on the stellar and gas disks?

(4) When the infall is near edge on the stellar and gas disks and rotation curves develop asymmetries: the side of the disk facing the external field becomes more compact than the far side, and the RCs become asymmetric around the galaxy’s center of mass.

4. What is the role of the cosmological hydrodynamical model in overcoming degene?

Overcoming these degeneracies will require improvements in the resolution, accuracy, and predictive power of cosmological hydrodynamical simulations, as well as inference frameworks that incorporate more sophisticated models for baryonic effects.

TABLE III. Summary of tests of modified-gravity enabled by current and future surveys.

FIG. 16. Excluded region in the χ-α plane derived by comparing Cepheid and TRGB distance estimates to 22 unscreened galaxies. The black dashed line corresponds to fðRÞ theories. Recall that fR0 ¼ 2χ=3. From Jain, Vikram, and Sakstein (2013).

FIG. 13. (a) Comparison of the fifth-force (y-axis) and normal GR (x-axis) contributions to the total force felt at particle locations in Nbody simulations of the nDGP model. The four panels split the particles by the type of cosmic web structure [halos, filaments, walls, and voids, as identified by the ORIGAMI algorithm (Falck, Neyrinck, and Szalay, 2012)] where each particle lies. The solid line marks the unscreened linear expectation, which is followed in filaments, walls, and voids; in the higher-density haloes, the fifth force is suppressed. From Falck et al., 2014. (b) Differential surface mass density (which is related to the lensing shear) of spherically symmetric stacks of voids in the cubic Galileon model. Relative to the GR scenario (red lines; named QCDM because the background is not ΛCDM), the full model result (blue lines) displays roughly the same enhancement as a linearized unscreened version of it (green lines). This indicates that the screening mechanism is not at play and thus that the fifth force can have prominent observational signatures. From Barreira, Cautun et al., 2015.

FIG. 8. A comparison of the ratios of power spectra for fðRÞ models and an equivalent ΛCDM model for jfR0j ¼ 10−4 (top panels), 10−5 (middle panels), and 10−6 (bottom panels) at z ¼ 0 (left-hand column) and 1 (right-hand column). We show the power spectrum from the simulations of Li, Hellwing et al. (2013) (blue points) together with that from two versions of the halo model, that of Mead et al. (2015) (short-dashed black lines) and Mead et al. (2016) (solid black lines). The former does not take into account chameleon screening and thus overestimates the deviation from GR. We also show the MG-HALOFIT model (Zhao, 2014) (long-dashed red lines) that was fitted to the same simulation data as shown (among others) and provides a better fit. From Mead et al., 2016.

FIG. 19. A galaxy falling into an external Galileon field ϕext. In the rest frame of the galaxy, the SMBH feels two forces: the outward Galileon force and the restoring force of the baryons left at the center.

FIG. 20. Left panel: restoring force profile for a cored galaxy (red solid line). The blue dashed, upper line shows the case where the Galileon force exceeds the maximum restoring force and the black dotted, lower line shows the case where the Galileon force is smaller than this. In the latter case, there are two equilibrium positions labeled 1 and 2. The former point represents a stable offset; the latter is unstable. Right panel: restoring force for a cusped (NFW) profile (red solid line). The blue dashed, upper line shows the case where the Galileon force is larger than the maximum restoring force (the force at the center) and the black dashed, lower line shows the case where it is smaller than this.

Citations

Monthly Notices of the Royal Astronomical Society

Paul Murdin

- 01 Jan 2005

TL;DR: The Monthly Notices as mentioned in this paper is one of the three largest general primary astronomical research publications in the world, published by the Royal Astronomical Society (RAE), and it is the most widely cited journal in astronomy.

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Annual Review of Nuclear and Particle Science

John David Jackson, +9 more

- 01 Dec 1984

TL;DR: In a recent review as mentioned in this paper, the authors reflect some of the shifts of emphasis that are occurring among the fields of astrophysics, nuclear physics, and elementary particle physics and discuss the role of rotational degrees of freedom in heavy-ion collisions at low and moderate energies.

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•Journal Article•10.1016/j.newar.2022.101659

Challenges for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="d1e11224" altimg="si239.svg"><mml:mi mathvariant="normal">Λ</mml:mi></mml:math>CDM: An update

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- New Astronomy Reviews

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Ultra-light dark matter

Elisa G. M. Ferreira, +1 more

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27 Jun 2022

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Novel Probes Project: Tests of gravity on astrophysical scales

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Most frequently asked questions

1. What contributions have the authors mentioned in the paper "Novel probes project: tests of gravity on astrophysical scales" ?

2. What can be done to slow down the decay of the gravitational potential?

3. What is the effect of a face-on infall on the stellar and gas disks?

4. What is the role of the cosmological hydrodynamical model in overcoming degene?

5. How does the speedup trick affect the performance of the algorithm?

6. What is the main reason for the voids to become more efficient?

7. What is the first challenge facing the utility of voids as a cosmological probe?

8. How do you get the leading-order correction to the linear power spectrum?

9. What are the common types of redshift fitting codes?

10. What is the way to improve the performance of the DGP simu-lations?

11. What is the way to enforce a near cancellation of a gravity theory?

12. What are the advantages of distance indicators for chameleons?

13. What is the minimum mass for which the star can burn hydrogen?

14. What are the parameters used to constrain the deviations of gravity in the linear regime?

15. What is the way to rule out the finely tuned models of this kind?

Figures

Citations

Monthly Notices of the Royal Astronomical Society

Annual Review of Nuclear and Particle Science

Challenges for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="d1e11224" altimg="si239.svg"><mml:mi mathvariant="normal">Λ</mml:mi></mml:math>CDM: An update

Ultra-light dark matter

From Galactic Bars to the Hubble Tension: Weighing Up the Astrophysical Evidence for Milgromian Gravity

References

Planck 2018 results. VI. Cosmological parameters

GW170817: observation of gravitational waves from a binary neutron star inspiral

The Structure of cold dark matter halos

Planck 2018 results. VI. Cosmological parameters

The Cosmological Constant Problem

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