Table Of ContentProceedings:EvolutionofLargeScaleStructure–Garching,August1998
BROKEN DEFECTS
Ue-LiPen1
1CITA, 60 St. George St., Toronto, M5S 3H8, Canada
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9
9 ABSTRACT.Recentindicationsofaneutrinomassraisethepossibilitythat
1 thedarkmattermaybehot,whichwouldbeaseverechallengeforstructure
n formationtheory. Wearguethatgenericdefect theoriesfareverywellinhot
a dark matter cosmologies, and also work in the presence of curvature or a
J cosmologicalconstant.Ifthismodeliscorrect,thentheMAPandPLANCK
missionswillnot measure what people expect them to (oscillations); rather,
6
theywillmeasureabroadhump.
2
1
v Thetraditionalclassofscalein- most recent supernovae search[4,
7 variant defect models has severe 5], concordance arguments[6] and
5 problems[1, 2]. They do not ex- direct angular diameter distance
3
plain the rise in fluctuation am- measurements[7] have suggested
1
plitudeat scales of a few degrees, that the universe is filled with a
0
andtheslopeoftheperturbations cosmological constant. This fur-
9
is at conflict with the observed ther challenges hot dark matter
9
/ matterpowerspectrum.Weshow (HDM)structureformation mod-
h here that global topological de- els,butwillturnouttobesimple
p
fectsgenericallychangebehaviour to reconcile in defect models.
-
o atthematter-radiationtransition Letusnowaddressthedynam-
r at a cosmic age of 100000 years. ics of global defects at matter-
t
s In this case, instead of being at radiation equality. In modern
a great discrepancy with the cos- particle physics, all interactions
v: mic microwave background ra- which are not forbidden actu-
i diation fluctuations, this model ally occur. On this ground, one
X
in fact correctly explains several generically expects couplings be-
r hitherto mysterious phenomena. tween gravity and other quan-
a
Recent measurements have indi- tumfieldswhicharestrongerthan
cated that neutrinos have mass, justminimalcouplingtothespace
andhaveopenedupthatthedark time curvature. Global fields ex-
matter may be massive neutri- perience couplings of the form
nos. If we accept that neutri- ǫφ†1φ2R, where ǫ is a dimension-
nos have mass, we have the po- less coupling constant of order
tential consequence that neutri- unity, and R is the scalar cur-
nos account for all the dark mass vature. Einstein equations relate
in the universe. This simple sce- R=T =ρ−3p. In the radiation
nario is consistent with the sim- epoch of the universe, R = 0, so
plest massive neutrino extensions thecouplinghasnodynamicalef-
of the standard particle physics fect.Butwhentheuniverseenters
models[3], and challenges cosmol- matter domination, this coupling
ogists to contemplate its implica- will generally modify the symme-
tionsforstructureformation.The trywhichgaverisetothedefects,
scale invariant adiabatic model andtheycanchangetheirdynam-
predicted by inflation is not con- ics. During the onset of change,
sistent if massive neutrinos ac- thevacuumenergycontributedby
count for the bulk of gravitat- the new coupling will boost the
ing matter. We will show that power on the largest scales, mak-
generic defect models would now ingthepowerspectrumconsistent
become the best physically based with the observed excess of large
modelofstructureformation.The scale power.
2
These defect models have two matter power spectrum. In simu-
free parameters. One is the sym- lations wehaveobservedthat the
metry breaking scale φ0, and the onset of the phase transition at
second is its coupling to the Rie- matterradiationequalityfurther-
mann scalar ǫ. From the velocity moreinjectspoweratthehorizon
dispersion in clusters of galaxies scale at that time, or about 100
we expect φ0/mplanck ∼ v2/c2 ∼ Mpc scales[14].
10−5, which would also be re- Inthedefectscenario,thesmall
lated to the COBE fluctuations. scale CMB experiments MAP
This energy scale suggests that and Planck will not measure
the defect would be relicts of the the multiple oscillations expected
breaking of the Grand-Unified- from adiabatic perturbations im-
Theory in the early universe. A printed before the big bang, as
predictive property of this model predicted by inflation. Instead,
is the non-Gaussianity of fluctu- the degree scale anisotropies are
ations. The strongest constraints caused by the incoherent prop-
arises from the statistics of rich erties of global defects[2]. With-
clusters[9]. Several clusters with outtheoscillations,itwillbevery
temperatures above 12 keV have difficulttoreconstructcosmologi-
beenfound[10],andarecentclus- calparametersaccurately.Onthe
ter with a temperature of 17 other hand, this would be an ex-
keV[11] has been discovered. The citing measurement of fundamen-
existence of these very hot clus- talphysicsandthehistoryofsym-
ters is becoming an enigma for metry breaking.
anyGaussiancosmologicalmodel.
In non-Gaussian defect models,
onewouldexpectalargerpropor- Acknowledgements
tion of high temperature clusters
relative to low temperature ones. . The idea of broken scale in-
The recent Las Campanas galaxy variance from non-minimal cou-
survey discovered features in the plingisduetoNeilTurok.Ithank
two dimensional galaxy power Uros Seljak for helpful discus-
spectrum which is inconsistent sions.
with Gaussianity[12]. Such signs
ofnon-Gaussianityaregenerically
predicted in these defect models. References
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