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Modified Gravity for Universe's Acceleration: A Gravitational Shortcut

Explore Gia Dvali's work on Modified Gravity versus Dark Energy at New York University, analyzing the universe's acceleration and the need for dark energy. Discover the lunar ranging test of modified gravity and the implications of constant curvature on graviton condensate. Uncover how massless bosons can condense in modified gravity, leading to a self-accelerating Universe. Delve into the Friedman equation for flat and empty universes and understand the implications of acceleration at a constant rate. Learn more about the fascinating relationship between gravity modification and the acceleration of our cosmos.

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Modified Gravity for Universe's Acceleration: A Gravitational Shortcut

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  1. LARGE DISTANCE MODIFICATION OF GRAVITY Gia Dvali New York University

  2. Modified gravity versus dark energy Dvali, Gabadadze, Porrati; Dvali, Gabadadze; Deffayet, Dvali, Gabadadze; Dvali, Gruzinov and Zaldarriaga; Dvali, Turner; Modified Gravity and Cosmological Constant Dvali, Gabadadze, Shifman; Adams, McGreevy, Silverstein; Arkani-Hamed, Dimopoulos, Dvali, Gabadadze

  3. Universe’s acceleration: Hubble parameter: Friedmann equation (flat universe) Dark energy or Modified Gravity?

  4. Gravitational shortcut

  5. 8 3 H2-H/rc = GN FRW Equation is modified Early cosmology in normal H>>rc-1 Late cosmology HH=rc-1 At late times Universe is self-accelerating! NO NEED IN DARK ENERGY.

  6. LUNAR RANGING TEST OF MODIFIED GRAVITY Predicted anomalous perihelion precession of the lunar orbit =1.4 x 10 -12 Todays accuracy: =2.4 x 10 -11 10-fold improvement is expected

  7. Why: modified gravity  universes acceleration? Universe’s acceleration at a constant rate implies: CONSTANT CURVATURE = GRAVITON “CONDENSATE” R = 12 H2 = constant Because of acceleration our Universe is filled with a minuscule nearly-constant graviton condensate ~ 10-29g/cm3 BUT, MASSLESS BOSONS DO NOT CONDENSE WITHOUT A SOURCE This is why in Einstein’s gravity the Universe’s acceleration requires a dark energy source!

  8. But, in modified gravity gravitons are no longer massless, and can condense without any dark energy source! Resulting into the self-acceleratedUniverse Friedmannequationfor flat and empty universe: H2 = 0  No expansion Modified Friedmann equation for flat and empty Universe: H2 - H/rc= 0  Acceleration at a constant rate: H=1/rc

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