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Phantom Energy with variable G and

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It is postulated in 2003 by Caldwell to account for the ... Quintessence (-1 w -1/3) Domain Walls (w = -2/3) Cosmic Strings (w = -1/3) Phantom (w -1) ... – PowerPoint PPT presentation

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Title: Phantom Energy with variable G and


1
Phantom Energy with variable G and ?
  • Arbab I. Arbab
  • University of Khartoum
  • Sudan
  • 4th International Workshop on Dark Side of the
    Universe
  • 1-5 June 2008, Cairo, Egypt

2
Phantom Is a hypothetical form of energy
that has an equation of state such that w lt-1.
It is thus a form of Dark energy. It is
postulated in 2003 by Caldwell to account for the
present acceleration of the universe.Some data
claim that today -1.62 lt w lt -0.74 (Caroll et
al.)
  • Dark energy candidates are numerous
  • Cosmological Constant (w -1)
  • Quintessence (-1 lt w lt -1/3)
  • Domain Walls (w -2/3)
  • Cosmic Strings (w -1/3)
  • Phantom (w lt -1)

3
  • Supernovae type 1a indictae that the universe
    today is accelerating. Faster rates are also not
    excluded.
  • Thus phantom energy is the most likely acceptable
    candidate (w lt -1)

4
Phantom Model (Scalar field)
5
  • These models state that in a finite time in the
    future the scale factor becomes infinite, and
    that the energy density becomes infinite too.
  • When phantom intervenes the solar sysytem, milky
    way or a nucleus it explodes it (Big-Rip).

6
Cosmological Constant (vacuum related)
  • We present here a model in which
    , const.
  • However, we allow ? and G to vary with time in
    such a way that the variation of ? is cancelled
    by the variation of G.
  • This entitles that the energy conservation
    equation formally looks the same as in standard
    FLRW model.
  • The above equation together with Friedman
    equations yield

7
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8

9
Dark Energy models
  • Cosmic acceleration with ordinary matter is
    possible
  • Cosmic expansion with other forms requires that

10
Inflationary Solution
  • Inflation in this model is obtained when
    ( i.e., ) and w
    -1, and with as in the standard de
    Sitter model, i.e.,
  • where, Hconst. and

11
ConclusionS
  • Our model shows that phantom energy requires a
    negative gravitational constant (i.e., G lt 0) and
    a positive cosmoloogical constant ( ).
  • Expansion is pushed by antigravity of the phantom
    energy and the vacuum decay. This is why
    acceleartion is faster than usual.
  • Other forms of cosmic acceleration are also
    possible.

12
Thank you.-----------------------Special
thanks to the DSU organizers for hospitality and
financial support.
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