Transcript Magnetic Monopoles - University of California, Berkeley

MAGNETIC MONOPOLES
Andrey Shmakov
Physics 129 Fall 2010
UC Berkeley
OVERVIE
W

Dirac Monopoles
Appeal to symmetry
 Quantum Mechanical explanation


GUT Monopoles



Symmetry Breaking
Gauge Theories
Monopole Searches
Methods
 Experiments


Current Experimental Limits
Nothing!
 Graphs!

DIRAC
MONOPOLE
Angular Momentum of a test particle
around a magnetic charge:
The Dirac Relation:
DIRAC
MONOPOL
E
GUT
MONOPOLE

Symmetry is lost during phase transitions
Water: isotropic, full
Rotational symmetry
Ice: Crystal Lattice
With preferred axis
GUT
MONOPOL
E
GUT
MONOPOLE


Phase transitions cause topological defects
Causality forces distant regions to precipitate into
different states
ASIDE: GAUGE
INVARIANCE
We intuitively understand position, time,
rotational, and potential invariance
 These transformations are universal


What if our transformation was a smooth
function of space-time?
ASIDE:
GAUGE
INVARIANCE
http://www.vttoth.com/gauge.htm
UGH!
Let’s Try that again
✔
http://www.vttoth.com/gauge.htm
EXPERIMENTALISTS!
MEET MR MONO POLE!

Charge:

Coupling constant:

Mass

Assume monopole classical radius ~ electron radius

GUT Mass depends on symmetry breaking
SEARCHES:
EXPLOITABLE
PROPERTIES
o Monopoles acquire energy in the galactic MF
oMonopoles can get trapped in ferromagnetic
materials, stopped in celestial bodies
o Interactions:
•High Energy: Behave like electrons:
synchrotron radiation, heavy energy loss, measurable
with scintillation counters.
•Slow Monopoles: ionizing radiation,
detectable
•Very Slow Monopoles: elastic collisions,
infrared radiation
•Interaction with superconducting magnets: regardless of
velocity
EXPERIMENTAL SEARCHES:
SQUIDS


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A magnetic monopole passing through a
superconducting loop will induce a very distinct
signal
Equally sensitive at all velocities
and monopole masses
Used to test materials for
embedded monopoles
EXPERIMENTAL
SEARCHES: TANTALIZING
CANDIDATES
On Valentines Day, 1982, a superconductin
induction coil detector recorded this
event
Phys Rev. Lett. 48 1378 (1982)
EXPERIMENTAL SEARCHES:
COSMOLOGY

Experiments are conducted to measure a flux of
magnetic monopoles that hit the earth as cosmic
rays
There are theoretical limits on the flux of heavy
MM from the galactic MF
 Monopole, Astrophysics and Cosmic Ray
Observatory (MACRO) searched for superheavy
MM in the beta < 1 range.

EXPERIMENTAL
SEARCHES:
COSMOLOGICAL LIMITS
EXPERIMENTAL SEARCHES:
DIRECT TESTS


Accelerators used to probe for possible light Dirac
monopoles
Tevatron collision exclude energies below 850GeV
EXPERIMENTAL
SEARCHES:
DIRECT TESTS
CONCLUSION
Monopoles are hypothetical, but predicted by the
most major theoretical models
 No confirmed repeatable monopole events have
been recorded
 Strong lower limits on energy place Dirac
monopoles out of reach of colliders
 Strong upper limits on cosmic ray flux


Maybe finding reason they don’t exist is more
interesting than finding them?