Dr Martin Hendry

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Why are we here?
Dr Martin Hendry University of Glasgow
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Why are we here?.
The period of inflation in the very early
Universe was invoked to explain some apparent
fine tuning problems.
If the Universe is now inflating, this presents a
new set of fine tuning problems
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State of the Universe Nov 2003
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State of the Universe Nov 2003
Why does 96 of the Universe consist of
strange matter and energy?
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From Lineweaver (1998)
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General Relativity- Geometry
matter / energy Spacetime tells matter how to
move and matter tells spacetime how to
curve Einsteins Field Equations
Ricci tensor
Einstein tensor
Metric tensor
Energy-momentum tensor of gravitating mass-energy
Curvature scalar
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General Relativity- Geometry
matter / energy Spacetime tells matter how to
move and matter tells spacetime how to
curve Einsteins Field Equations
Treating the Universe as a perfect fluid, can
solve equations to determine the pressure and
density, and how they evolve
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Einstein originally sought static solution but
this isnt possible, for normal pressure and
density He added a cosmological constant
to the field equations
Can tune to give static Universe, but
unstable (and Hubble expansion made idea
redundant anyway!)
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Einsteins greatest blunder?
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But what is ? Particle physics motivates
as energy density of the vacuum but
scaling arguments suggest- So historically
it was easier to believe
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Re-expressing Friedmanns Equations At any time
Dimensionless matter density
Dimensionless curvature density
Dimensionless vacuum energy density
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Re-expressing Friedmanns Equations At any
time If the Universe is flat then
Dimensionless matter density
Dimensionless curvature density
Dimensionless vacuum energy density
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State of the Universe Nov 2003
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State of the Universe Nov 2003
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From Lineweaver (1998)
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Value of
Present-day
If the Concordance Model is right, we live at a
special epoch. Why?
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Hydrogen fusion fuelling a stars nuclear
furnace
E mc
2
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P-P chain, converting hydrogen to helium
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This has led to more general Dark Energy or
Quintessence models Evolving scalar field which
tracks the matter density Convenient
parametrisation Equation of State Ca
n we measure w(z) ?
Pressure
Density
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SNIa at z 0.5
At low redshift, SN1a essentially measure the
deceleration parameter
Adapted from Schmidt (2002)
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SNIa at z 1.0
At low redshift, SN1a essentially measure the
deceleration parameter
Adapted from Schmidt (2002)
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SNIa at 0.5ltzlt1.0
At low redshift, SN1a essentially measure the
deceleration parameter
Adapted from Schmidt (2002)
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SNIa measure- CMBR measures- Together,
can constrain-
Tegmark et al (1998)
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Can we distinguish a constant L term from
quintessence? Not from current ground-based SN
observations (combined with e.g. LSS)
Adapted from Schmidt (2002)
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Can we distinguish a constant L term from
quintessence? Not from current ground-based SN
observations (combined with e.g. LSS) or from
future ground-based observations (even with LSS
CMBR)
Adapted from Schmidt (2002)
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Can we distinguish a constant L term from
quintessence? Not from current ground-based SN
observations (combined with e.g. LSS) or from
future ground-based observations (even with LSS
CMBR)
Adapted from Schmidt (2002)
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Can we distinguish a constant L term from
quintessence? Not from current ground-based SN
observations (combined with e.g. LSS) or from
future ground-based observations (even with LSS
CMBR)
Main goal of the SNAP satellite (launch 2010?)
Adapted from Schmidt (2002)