Transcript Dark Matter in the Universe

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DARK MATTER IN THE UNIVERSE
The Universe
 What do we know about it
 age: 14.6 billion years
 Evolved from Big Bang
 chemical composition
 Structures in the universe
 galaxy clusters
 galaxies
 voids
Separation of forces
 gravity
 strong force
 weak force
what causes interaction?
 gravity
 electromagnetism
 weak force
 strong force
Some particle physics
 Baryons: composed of three quarks
proton; the only long living hadron, t=1031s; measure for p
decay= test for GUT
 Mesons: composed of one quark and one
antiquark
 Baryons and mesons: hadrons
 Hadrons are composed of quarksstrong
interaction
 Leptons: no quarks, no strong interaction
Higgs particle, higgs field
 mass=interaction of a particle
 In empty space, the Higgs field has an
amplitude different from zero; i.e., a nonzero vacuum expectation value.
 The existence of this non-zero vacuum
expectation plays a fundamental role: it gives
mass to every elementary particle which has
mass, including the Higgs boson itself.
Galaxies
Clusters
Das galaktische Zentrum
La voie lactee
The solar neighborhood
Galaxis
200-400 109 Sterne
Durchm.: 100 000 Lj
Rotation: Ort der Sonne
etwa 200 Mill Jahre
Determination of the mass of
a galaxy
2
v
Mm
m G 2
r
r
Star
Galactic center
centrigual force
attraction
Solarsystem…
Merkury: 88 days
Earth: 1 year
Jupiter: 11,6 years…
Galactic rotation curve
v (R)
Kepler
Kepler Rotation of a Galaxy
1.2
1
velocity
0.8
0.6
0.4
0.2
0
0
2
4
6
8
distance from galactic center
10
12
Rotation of a galaxy
Rotation curve of NGC 3198
Kepler Rotation of a
Galaxy
velocity
1.5
1
0.5
0
0
5
10
distance from galactic center
15
Gravity lensing
Composite image of the Bullet cluster shows distribution of
ordinary matter, inferred from X-ray emissions, in red and
total mass, inferred from gravitational lensing, in blue.
properties of dark matter
 undetectable by radiation
 detectable only by gravitation
 rotation of galaxies
 orbital velocities of galaxies in cluster of galaxies
 gravitational lensing
 temperature distribution of hot gas in galaxies and
clusters of galaxies
what is dark matter made of
 majority: non baryonic
 non baryonic matter
 neutrinos
 axions
 supersymmetric particles
 does not contribute to the formation of elements
in the cosmos
non baryonic matter
 hdm hot dark matter: massive neutrinos
 cdm cold dark matter: will lead to a bottom
up formation of structure in the universe;
neutralino
 wdm warm dark matter
Neutralinos
 big bang: neutralino halos
 mass of Earth, size equal to the solar system
 can be detected:
 disturb Oort cloud  cometary showers
 produce gamma ray bursts when colliding
 more probable near galactic center
baryonic matter
 composed of baryons
 protons
 neutrons
 candidates for baryonic dark matter
 MACHOs: massive astropnomical compact halo
objects
 brown dwarfs (M<0.08 MSun
 amount can be calculated from
 big bang nucelosynthesis
 cosmic microwave background
MACHOS
 Detect: gravity bends light
 MACHO may be detected if it pass in front of
a star or nearby a star;  brightening of the
star
 candidates for MACHOS
 black holes
 neutron stars
 black dwarfs
WIMPS weakly interacting
massive particles
 interact through weak force and gravity
 do not interact through electromagnetism
 large mass, slow moving, cold particles
 could interact with the Sun, produce high
energy neutrinos
CDMS cryogenic dark matter
search
RAMBOs Robust associations of
massive baryonic objects
 dark cluster made of
 white dwarfs
 brown dwarfs
 radii: 1 pc … 15 pc
supersymmetry, susy
 In particle physics, supersymmetry (often
abbreviated SUSY) is a symmetry that relates
elementary particles of one spin to other
particles that differ by half a unit of spin and
are known as superpartners.
 In a theory with unbroken supersymmetry,
for every type of boson there exists a
corresponding type of fermion with the same
mass and internal quantum numbers, and
vice-versa.
Λ CDM Model of Cosmology I
 Λ cosmological constant  associated with
a vacuum energy or dark energy
 explains the current accelerating expansion of
space against the attractive (collapsing) effects of
gravity. ΩΛ, which is interpreted as the fraction of
the total mass-energy density of a flat universe
that is attributed to dark energy.
 Currently, about 74% of the energy density of the
present universe is estimated to be dark energy.
Λ CDM Model of Cosmology II
 CDM cold dark matter
 dark matter is described as
 cold (non relativistic)
 collisionless (only gravity forces)
 22% of the mass-energy density of the universe
quantum chromodynamics describes strong interaction