Download PowerPoint Presentation - Advanced Quantum Mechanics

Black hole
For large enough masses, as far as we know, nothing is stiff
enough to stop the collapse. It continues down to a singularity:
a defect in space and time.
Singularities
Singularities are points of infinite gravity, or
more accurately, infinite space-time curvature,
where space and time end.
They are a kind of boundary of the universe.
Light rays
emitted by star
Susan Scott
Singularity theory
Position
Particle paths in a
collapsing star
singularity
Event horizon
Time
Quantum Gravity & String Theory
Understanding singularities will require new
theories, probably combining General
Relativity with Quantum Mechanics.
One candidate is string theory. It assumes that
the basic structure of matter is string-like, not
point-like.
Although still speculative, it allows the direct
calculation of black hole entropy by counting
micro-states.
The event horizon
The singularity is
surrounded by an
event horizon.
This is the boundary
at which the escape
velocity is the speed
of light.
Consequently, nothing
can come out of the
event horizon, not
even light - hence the
name "black hole".
Gravity deflects light
Distant galaxies being imaged
by the Abell cluster
Gravitational lensing by
the Abell galaxy cluster
The effect of gravity on light
Relativity
implies
nothing
can go
faster
than light.
Evidence for black holes
A disk of dust fuelling a
massive black hole in the
centre of a galaxy, located
100 million light-years
away.
800 light years
The speed of the gas
swirling around the black
hole indicates that the
object at the centre of the
disk is 1.2 billion times
the mass of our Sun, yet
concentrated into a region
of space not much larger
than our solar system.
Black Hole at the centre of a galaxy
Gravity as curved space
Gravity as curved space
Space-time
“ The views of space and time which I
wish to lay before you have sprung from
the soil of experimental physics, and
therein lies their strength. They are
radical. Henceforth space by itself, and
time by itself, are doomed to fade away
into mere shadows, and only a kind of
union of the two will preserve an
independent reality”.
H. Minkowski, Speech, 1908.
Space-time
Spatial separation and time separation are not
individually fundamental: they depend on the
observer.
The geometric union of space and time into
4 dimensional SPACE-TIME is the
fundamental, observer independent, reality.
Falling into a black hole: observing
For a distant observer, time slows down for an object approaching
the event horizon. Objects approach it without ever passing through
it!
Falling into a super-massive black hole
For an observer falling into a big enough black hole nothing much
happens while falling through the event horizon. However the
"irresistible" flow of time is accompanied by an "irresistible" falling
towards the singularity - due to the mixing of space and time.
Falling into a stellar mass black hole
An observer falling into a stellar mass black hole
experiences huge gravitational gradients (tides) which
stretch vertically and compress horizontally.
Black hole evaporation
Quantum mechanics predicts that
space is filled with virtual particle
pairs.
If one falls into the black hole the
other gains its energy and
becomes real: this is the Hawking
radiation.
Black hole explosions?
The title of a 1974 paper by
Stephen Hawking.
The gravity at the event horizon is
inversely proportional to the hole's
mass.
1032 years
Hence Hawking radiation becomes
more intense as the black hole shrinks.
A black hole with the mass of an
asteroid is as bright as the Sun.