Modified Gravity vs. ΛCDM Roman Shcherbakov Astronomy 202b final presentation 12 December 2007.
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Modified Gravity vs. CDMRoman ShcherbakovAstronomy 202b final presentation12 December 2007
Dark parts should be illuminated /or/ eliminatedCDM
- Modified Newtonian Dynamics Proposed by Milgrom in 1983 Heavily criticized thereafterfor a>>a0for a
Other Modified Gravity ModelsSUper GRAvity (SUGRA) a candidate for the theory of everything
Modified Gravity & Tensor/Vector/Scalar theory by Moffat & BekensteinIn contrast to MOND these theories:Do not violate 3-d Newtons Law/conservation of momentum/ isotropy of space/Cosmological principleHave covariant description/equations are form-invariantSometimes linearHave physical reasons to exist
Tests on the scale of Solar systemPioneer anomalyKeplers Lawof planetary motionAdditional Solar-/Earth- ward acceleration for both spacecraftsExtreme relativistic pulsar PSR B1913+16
Tests on the scale of GalaxiesFlat rotation curvesRotation curves in dwarf Galaxies may require different fit parametersUnusual shape and high velocities in Bullet Cluster
Tests on cosmological scaleStructure formation, no Silk dampingRelative height of first CMB peaksPrimordialnucleosynthesisAccelerating expansion of the Universe?
ConclusionsPeople are not always critical about their work careful comparisons should be madeHuge number of observational tests should be explained by alternative theories: the circle of possible models is shrinkingMOND violates isotropy of space, linearity, covariance and may not be used to fit any dataGeneral Relativity on the scale of Solar system + Pioneer anomaly => weak constrains on modified gravity modelsFlat rotation curves => either dark matter /or/ scale-dependent modification of gravityStructure formation => presence of some dark matter component even for models with modified gravitySome modified gravity models (e.g. that by Moffat) may be as good as CDM model in sum over all the tests. Additional research/more tests are needed.
BibliographyBekenstein J., Milgrom M. 1984, ApJ, 286, 7Moffat, J. W. 2006, J. of Cosm. and Astropart. Phys., 004Moffat, J. W., \& Toth, V. T. 2007, astro-ph/0710.0364v3Brownstein, J. R., Moffat, J.W. 2006, Class. Quantum Grav., 23,3427Milgrom M. 1983, ApJ, 270, 365Milgrom M. 1983, ApJ, 270, 371Scott D., Martin W., Cohn, J. D., Pierpaoli E. 2001, astro-ph/0104435v1Turyshev, S. G., Nieto, M. M., Anderson. J. D. 2005, gr-qc/0510081