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Related Concept Videos

Variation in Acceleration due to Gravity near the Earth's Surface01:20

Variation in Acceleration due to Gravity near the Earth's Surface

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Modifying gravity: you cannot always get what you want.

Glenn D Starkman1

  • 1Department of Physics, Center for Education and Research in Cosmology and Astrophysics, and Institute for the Science of Origins, Case Western Reserve University, Cleveland, OH 44106, USA. gds6@cwru.edu

Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
|November 16, 2011
PubMed
Summary
This summary is machine-generated.

Modified gravity theories aim to resolve discrepancies between general relativity and observations without invoking dark matter. However, these theories face significant challenges, potentially requiring them to incorporate dark matter-like components themselves.

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Setting Limits on Supersymmetry Using Simplified Models
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Setting Limits on Supersymmetry Using Simplified Models
07:46

Setting Limits on Supersymmetry Using Simplified Models

Published on: November 15, 2013

Area of Science:

  • Cosmology and astrophysics
  • Theoretical physics
  • Modified gravity theories

Background:

  • General relativity and the Standard Model face observational discrepancies.
  • The Lambda cold dark matter (ΛCDM) model introduces dark energy, dark matter, and inflaton, but lacks direct evidence.
  • Alternative approaches explore modifications to general relativity to explain these phenomena.

Purpose of the Study:

  • To analyze the challenges faced by modified gravity theories attempting to replace dark matter.
  • To evaluate the viability of modified gravity as an alternative to dark matter.
  • To explore the potential for modified gravity to necessitate its own dark matter components.

Main Methods:

  • Review and discussion of theoretical challenges for modified gravity models.
  • Analysis of covariant realizations of modified Newtonian dynamics.
  • Examination of specific issues: Birkhoff's theorem, cluster dynamics, and cosmological expansion effects.

Main Results:

  • Modified gravity models face significant hurdles, including the loss of Birkhoff's theorem and difficulties explaining galaxy clusters.
  • These theories may require the introduction of dark matter-like components (e.g., neutrinos, dark fields) to reconcile with data.
  • Cosmological expansion intrudes into modified force laws due to scale coincidences.

Conclusions:

  • Replacing dark matter with modified gravity presents substantial theoretical and observational challenges.
  • Modified gravity theories may paradoxically evolve into or incorporate dark matter theories.
  • Further research is needed to assess the feasibility of modified gravity in light of current cosmological data.