Brownsberger, Kramer, Rowan, Xu Whats post-modern? As with particle - - PowerPoint PPT Presentation
LR w/ Fan, Katz, Reece Agrawal, Cyr-Racine, Scholtz, Brownsberger, Kramer, Rowan, Xu Whats post-modern? As with particle physics, easy times are probably at an end Need to look at subtle effects Basically (as with SM) CDM SM
As with particle physics, easy times are probably at an
Need to look at subtle effects Basically (as with SM) ΛCDM SM essentially works But we don’t know if it’s whole story Several things I’m working on (which to present?)
Black hole mergers and what they can tell you Hubble expansion: most interesting discrepancy! ** Dark matter: how to find what it is from astronomical
measurements
Compact objects or particle If a particle, what is it
Mass, interactions?
If not a WIMP, can we observe its consequences?
Astronomical MEASUREMENTS AND STRUCTURE
Our program:
Propose models
Systematic exploration of simple possibilities
Analytic and numerical predictions Make measurements
Emphasize could be ONLY way we learn about dark matter’s
identity
Dark matter that interacts with itself
Not necessarily with ordinary matter
Has testable consequences Might even address issues with CDM How to pursue this theoretically? And determine consequences?
Simple idea: Assume dark matter charged under its own
“electromagnetism”: “dark light”
Dark matter charge, U(1)
Could be light and heavy (like proton and electron) Could be just heavy dark matter candidate (and antiparticle)
Thought to be very constrained
Even though NOT a WIMP
Turns out can be weak scale mass with EM-type coupling Or if a fraction of dark matter can be even less constrained
Dark matter with its own force
Rather than assume all dark matter Assume it’s only a fraction
Maybe like baryons? Nonminimal assumption But one with significant consequences
Will be tested Leads to rethinking of implications of almost all dark matter,
astronomical, cosmological measurements
Since we don’t know what dark matter is
Should keep an open mind Especially in light of abundance of astronomical data
Dark “proton” aka Charged WIMP gD Aµ
D X γµ X
+Dark electron gD Aµ
D C γµ C
+Kinetic Mixing -ε/2 FD
µνFµν
freezeout
spectrum
recombination
Dark matter charged under its own “electromagnetism”
Ellipticity of halos Bullet Cluster type constraints Survival of dwarf galaxies in halos (lack of
Seemed to significantly impinge on parameter space
Ellipticity of halos Bullet Cluster type constraints Survival of dwarf galaxies in halos (lack of
Seemed to significantly impinge on parameter space
Galaxy ellipticity was strongest constraint Ellipticity tricky to calculate It’s a function of radius And only one galaxy measured anyway Dwarf galaxy survival calculation different when
Bullet cluster relies on initial distributions
Constraints on mass considerably weaker than stated Not yet reliable
Simulations can help
Exciting possibility that dark matter has its own world
And that conceivably we can detect them Weak mass particles with even EM-type strength
Nonminimal assumption: why would we care? Implications of a subdominant component
Can be relevant for signals if it is denser
Baryons matter because formed in a dense disk
Perhaps same for component of dark matter
Dark disk inside galactic plane Or Point sources after fragmentation Potentially significant consequences
Leads to rethinking of implications of almost all dark matter,
astronomical, cosmological measurements
Detectable!
Velocity distributions in or near galactic plane constrain fraction to be comparable or less to that of baryons
Further constraints from CMB
But because it is in disk and dense signals can be rich
Could be U(1) or a nonabelian group U(1)D, αD Two matter fields: a heavy fermion X and a light
For “coolant” as we will see
qX=1, qC=-1 (In principle, X and C could also be scalars) (in principle nonconfining nonabelian group) This in addition to dark matter particle that makes up
A heavy component Brehm and inverse Compton
For disk to form, require light component
With these conditions, expect a dark disk
Even narrower than the gaseous disk
Smaller direct detection, small velocity
Possibly other noncanonical possibilities
Indirect detection
Possible if mediation between visible, invisible sectors
Good thing there is distinctive shape to signal if present Best search: directly with GAIA data Use density, velocity measurements to deduce gravitational
potential
About half the satellites are approximately in a (big plane)
14kpc thick, 400 kpc wide
Hard to explain Proposed explanation: tidal force of two merging galaxies Fine except of excessive dark matter content Tidal force would usually pull out only baryonic matter
from disk
Not true if dark disk Pulls out dark matter
Slower velocity—more likely to be bound So even subdominant component in disk can be dominant in
dwarfs
w/Scholtz
Evidence for GeV excess Seems to come from point sources Argued that pulsars are the source Could also be point sources from COMPACT dark matter
Possible when dissipative! Dark photon leads to cooling Instabilities leads to compact objects Annihilations through Z’ lead to visible signals
Due to mixing with photon
Would appear as point sources
We consider the morphologies of dwarf spheroidals
the Local Group (LG). Ellipticities and associated 3-D shapes, and whether
Compare CDM- sourced simulations to observations
Dsphs: common, little gas, eqm stars determined from grav
potential
Simulations: prolate halos so we expect the stellar
distributions of dsphs sourced from CDM haloes should be likewise prolate. But how to deduce 3D structure when we make 2d
Expect the surface brightness of a prolate galaxy is anti-
correlated with its projected ellipticity, while the opposite is true of oblate galaxies.
Use this to deduce 3d structure
Role for particle physics approach in astronomy “constraint” on dark disk came from fitting standard
Turns out errors on standard components not properly
accounted for
Reddening important near midplane Has to be done self-consistently
Here different components influence each other through
gravity
Big messy data sets Targeting a model helps
Very interesting new possibility for dark matter
That one might expect to see in observations
ard to know whether or not it’s likely
How much should dark matter resemble SM But not be part of it
But presumably would affect structure
Just like baryons do Research area
Rich arena: lots of questions to answer