Summary Talk: Cosmology and Gravitation
Ioav Waga
UniversidadeFederaldoRio deJaneiro,Institutode Fsia
C. P.68528, 21945-970,Brazil.
Reeivedon14February,2001
TheworksonCosmologyandGravitationpresentedduringtheXXIBrazilianNationalMeetingon
PartileandFields(BNMPF)arebrieyreviewed.
I Introdution
TheBrazilianNationalMeetingonPartileandFields
(BNMPF)isertainlyoneofthemostimportantannual
sientieventsinBrazil. Itbringstogethermorethan
250 researhersworking in the areaand, speially for
graduatestudents,itisanexellentshoolandagreat
opportunity to present and disuss work done and in
progresswithabroadaudiene.
As onerns the number of partiipants and
pre-sentations,Cosmologyand Gravitationis traditionally
the seond sub area of the BNMPF. Field Theory is
the rstone. Duringthe XXImeeting atotalofforty
sixworksinCosmologyandGravitationwerereported.
The numberoftotalpresentationsduring thelast ve
yearswasroughlythesame. Thisyear,however,dueto
modiationsin theseletionriteriaofthesubmitted
works, the number of panels surpassed the oral ones.
Wehad16oralommuniationsand30panels.
Is theBNMPF representativeof theresearh done
in GravitationandCosmologyin Brazil? Ibelieveitis
veryrepresentativeoftheresearhdoneonGravitation,
mainly if we onsider theworks presented during two
or three onseutive years. The emphasis of the vast
majorityofthe presentationsis theoretialbut we are
beginning to witness a welome hange with
inreas-ing numberofexperimental andmore
phenomenologi-al works. Besides theBNMPF meeting(that is
orga-nized bytheBrazilianPhysialSoiety),theBrazilian
Astronomial Soiety (SAB) also organizes an annual
meting. Therefore,in Cosmologytheresearhisnotso
representative(asin Gravitation)ofthetotalityofthe
ommunity work, sine some researhers working, for
instane, in extragalatiastronomy, preferto present
their worksin theSAB meeting. I believeitwouldbe
interestingifweouldndwaystodiminishthisgap.
OnCosmologyandGravitationwehadoneplenary
agogialplenary talk, R. H. Brandenberger presented
a review of the inationary senario. He emphasized
reent progresses done and outlined some oneptual
problems that still remain in inationary osmology.
Withonsiderabledetail,hedisussedtheroleof
para-metri resonane in the reheating phase at the end
of ination. He onsidered the utuation problem,
orthe neessity to ne tune aparameter in potential
driven ination to make theory ompatible with
ob-servations. The ne tuning is neessary in order to
haveasuÆiently smallamplitude ofthemass
utu-ation orresponding to somewavelength , when this
mode re-enters the Hubble radius. He also disussed
the trans-Plank-sale physis problem (that appears
insomemodelsof ination)and theosmologial
on-stantproblem that is evenmore severein inationary
osmologythanusually[1℄.
R. Opher presented a provoative parallel talk
where he ritially disussed the role of dark matter
inCosmology[2℄. Theideaofdarkmatterappearedin
the30'swhenF.Zwikysuggestedthatgalaxylusters
should have alarge amount of matter in some
nonlu-minous form. Sine then the searh for this
ompo-nent in large and galati sales has dominated
os-mology. However,after more thansixty years the
ex-at nature of the dark matter is still unknown. For
instane, the bulk of it an not be baryoni.
Stan-dardBig-Bang nuleosynthesisis notompatible with
the total amount of dark matter inferred from large
sale observations being baryoni. More reently, the
veryexistene ofdark matteris beginningto be
hal-lengedby someosmologists. Their motivation is the
following. Although inationary old (at deoupling)
dark matter (CDM) models with a osmologial
on-stant suessfully explain the large sale struture of
theUniverse, the osmi aelerationand the Cosmi
ob-models seemnotbeableto aountfor. Forinstane,
highresolutionsimulationswithollisionlessdark
mat-tershowuspyhalodensityproles,whileobservations
indiate uniformdensityproles. Further,these
simu-lations alsoshowmuhmoresub-struturein thehalo
ofatypialgalaxythanobserved. There areurrently
twowaystodealwiththeseproblems. Oneistoassume
that dark matter is self interating. A andidate for
self-interating dark matter issuggested, for instane,
inref. [7℄. Amoreextremepossibilityistomodifythe
Newtonian fore law for small aelerations as in the
modied nonrelativisti dynamis (MOND) suggested
by Milgrom morethan fteen years ago. Opher took
thelaterpointofviewandIdirettheinterestedreader
toseehis ontributioninthisvolume[2℄.
Finally,intheseondparallelsetionW.Wang
dis-ussedritialphenomenain gravitationalollapse[3℄.
II Cosmology
AtotalofsixteenpresentationsonCosmologywere
ex-hibitedduring themeeting. Almost halfof them were
relatedtodierentaspetsoftheinationarysenario.
In three projets, developed by I. D. Soares, H. P.
Oliveiraandollaborators,thedynamis ofa
preina-tionary phase of the Universe, and apossible haoti
exit to ination are investigated [4℄. In other three
works J. A. S. Lima, J.M. F.Maia and ollaborators
analyzedsomethermodynamispropertiesof
ination-ary models, speially during the reheating phase and
deation[5℄. A. MaiaJuniorand F.R.V. B.deMelo
alsoonsideredthepossibilityofexponentialgrowthof
partileinaregimeoutofparametriresonane.
Wehadthreeworksonstrutureformationand
per-turbationtheory. M. Makleret al. showed a
ompar-ativeanalysisof fourloal Lagrangianapproximations
forthenonlinearevolutionoflargesalestrutures[6℄.
V. T. Zanhinet al. derived equations desribingthe
growth of energy density perturbations for a lass of
-deayingosmologies anddisussed someproperties
ofthemodels. Astudy ofhowthesoftwareMaple an
helpinobtainingorretequationsofperturbation
the-orywaspresentedbyM.G.C.Batista.
In the interfae between partile physis and
os-mologywehadtwoworksbyR.Rosenfeld and
ollab-orators. Intherstoneasalargaugesingletoupled
totheHiggsbosonissuggestedasaandidatefor
self-interating darkmatter [7℄. Ina seond presentation,
nowwithL.L.Lengruber,byusingthedeteteduxof
ultrahigh energy osmirays,and twodierent
mod-els forthe X partile distribution,they obtained
on-straintson , M and h 2
.
Bytakingintoaountorretionsduetolinear
de-viations from the Hubble ow, Calv~ao et al. showed
thattheAlok-Pazynskitest,asappliedtothequasar
orrelationfuntion,isapowerfultesttoonstrain
os-mologial parameters. The method of Cosmi
Crys-tallography applied to inomplete atalogs of osmi
soureswasalsodisussed byA. Bernui[8℄.
On mathematial osmology two works were
pre-sented. M. L. Bedran et al. generalized the Mattig's
equation for a single uid with an equation of state
of the form p =w. G. Oliveira-Neto showed a
solu-tiontotheEinsteins'sequationsin2+1-dimensionsfor
aspaetimewithline symmetryandwherethematter
ontentisamasslesssalareld minimally oupledto
gravity.
III Gravitation
Thirtyworks ongravitation wereexhibited during the
meeting. Thisrepresents2=3ofthetotalworks
pre-sentedin thearea. Oneimportantprojet,leadby O.
D. Aguiar, is the GRAVITON projet. It has
seven-teen membersandollaboratorsfromseveralBrazilian
researh institutes(INPE, IFUSP, ITA, UNIBANand
CEFET)andonememberfromLeidenUniversity
(Hol-land). The goal of the projet is to build a spherial
resonant mass antenna to detet gravitational waves.
In the rst phase of the projet, the Mario
SCHEN-BERG detetor will be built. It will have a radius
r60m,massM 1200kgandwilloperatein very
low temperatures(15 20 mK).It willbesensitiveto
waves in the bandwidth 3:0 to 3:4 kHz of quadrupole
modes that arriveonearth with amplitudeh>10 22
Hz 1=2
. Inthisbanditssensitivitywillbeomparable
orevenbetterthanthosefrom largelaser
interferome-ters(as LIGOandVIRGO). Twosimilarantennasare
also being built, onein Frasati(Italy) and theother
one in Leiden (Holland). One ofthe main advantages
of the detetor is that it will be possible to loalize
the gravitational soure as well as the wave
polariza-tion. Possiblesoures to be deteted are: supernovae
ollapse, quakesand neutronstarsosillations,
exita-tionsofquasi-normalquadrupolemodes ofblakholes
withmass3:8M
andoaleseneofneutronsstars
andblakholes.
Three works were presented by the GRAVITON
group. The rstphaseof the projetwasreported by
O. D. Aguiar. C. Frajua onsidered three dierent
kindsoftransduersand disussedthereasonwhythe
indutivesuperondutingoneisthebestoptionforthe
projet. L.A. Andrade etal. alulated theexpeted
to optial transduers. Two related theoretial works
werepresentedbyF.Kokobunandollaborators.
Seven works ontopologial defets,showing
dier-entaspets ofhowondensedmatter anbea
labora-tory forgravitationwere reportedduring themeeting.
This interesting subjet is urrently being developed,
mainly, in twouniversities loated in thenortheastof
Brazil (UFPe and UFPb). For a review see ref. [9℄.
Also on gravitational analogsV. A. De Loreni et al.
disussed some geometrial aspets of nonlinear light
propagation[10℄.
Theonsistenyofgeometrodynamisandquantum
eld theoryintheBohm-deBroglieinterpretationwas
disussed by E. S. Santini and N. Pinto-Neto [11℄. A
mini-reviewwaspresentedbyM.D.Maiaonthe
quan-tumtheoryofBrane-worlds[12℄. V.Mostepanenkoand
M.NovelloonsideredaYukawatypeorretiontothe
Newtoniangravitationalpotentialoftheform:
V(r
12 )=
GM
1 M
2
r12
(1+e r12=
).
Sometheoriespreditsuhamodiationtothe
New-tonian law in submillimeter range. In their work the
appliation of the Casimir eet to onstrain the
pa-rametersandisdisussed[13℄.
Anewmetrinonsymmetriuniedtheoryof
grav-itation and eletromagnetismwaspresentedbyS.
Ra-gusa. Itwasobtainedbyrequiringthat,independently
of thevalueof anewuniversal onstantpresentin the
theory,theusualMaxwelltypeofequationsappearfor
the antisymmetri part of the metri g
[℄
in the at
spaelinearapproximation[14℄.
D. Muller and R. Opher investigated the orbitsin
MOND theory within a dwarf galaxy (M
d 10
8
M
)
atadistane100kpfromaneighboringgalaxysuh
asours(M
f 10
11
M
). Byusingthenumerial
teh-nique ofsurfaes ofsetiontheyanalyzedthestability
of thephase-spaeorbitsin thedwarfgalaxy[15℄.
L.C.T.Guillenetal. obtainedaonserved
energy-momentum gaugeurrentfor thegravitationaleld in
theontextoftheteleparallelequivalentofgeneral
rel-ativity [16℄. Byrewriting thegaugegravitationaleld
equations, they showed that they beome Einstein's
equations and that the gauge urrent redues to the
usual energy-momentum pseudotensor of the
gravita-tional eld.
Two works were reported in lassial eld theory
of spaetime. F.Parisioand F.Moraes disussedhow
magneti eld an ontrol exoti matter in a speial
kind of wormhole. S.E.P. Bergliaa and K. E.
Hib-berdinvestigatedtherestritionsthatanaxisymmetri
and stationaryspaetime shouldsatisfyto havea
per-fet uid as soure of urvature. They showed that
notbe desribed by aperfet uid orby a uid with
anisotropistresses[17℄.
Fourworksonquantumeldtheoryinurved
spae-time were presented during the meeting. D. A. T.
Vanzella and G. E. A. Matsas investigated the
inu-ene of gravity on quantum proesses whih our in
theinteriorofneutronstars. Theyfousedtheir
analy-sisontheneutronizationproess,p +
e !n
e ,whih
isimportantinoolingofneutronstarswith
tempera-turesupto10 9
K.Byusingasemilassialapproah
andatwo-dimensionaltoymodel,theyshowedthatthe
gravitationaleldplaysanegligibleroleintheproess.
However,astheypointedout,inamorerealisti
alu-lationtheresultsmighthange[18℄. Thedynamisofa
masslesssalareldin Reissner-Nordstromspaetimes
wasinvestigatedbyC.Mendes[19℄. Entropyboundfor
arotatingsystemfromanti-deSitterblakholewas
re-portedbyB.C.Melgar[20℄. H.ChavezandL.Masperi
addressedthesatteringofaMajoranafermionbya
lo-alosmistring.
Three works on gravitational ollapse were
exhib-ited. By usingtehniques of qualitative theory of
dy-namial systems O. C. Castellani and H. P. Oliveira
investigated ritial phenomena in gravitational
ol-lapseinthetheoriesofRelativityandBrans-Dike. M.
C. de Lima et al. studied the struture of
Robinson-Trautman solutions of Einsteins's eld equations in
vauoforwhih theangulardependenyof themetri
funtions is not analyti. They showed that the
non-analytiityproduesnewphysialeets[21℄. Astudy
onthegravitationalollapseofperfetuidwiththe
ze-rothandseond kindsofself-similaritywere presented
byJ.F.VillasdaRohaetal..
Two more mathematial works were also
pre-sented. PropertiesoftheLevi-Civita solutionsoupled
with eletromagneti elds wasinvestigated by A. Y.
Miguelotiet al.[22℄, and thestudy of spaetime
stru-turefromWeylspinorsand CliordalgebrasbyR. da
RohaandJ.VazJr..
IV Conlusion
There is muh interestingativity in the areaof
Cos-mologyandGravitation. Thisisertainlythemain
on-lusionweangetfromtheXXIBNMPF.Thequality
of theworks presented during themeeting also shows
thatourommunity isbeomingmorematureand we
anfeel agrowingonern onmorephenomenologial
and observational questions. In this respet I would
liketoemphasizeagaintheimportaneoftheGRA
Aknowledgments
IwouldliketothanktheOrganizingCommitteefor
theinvitationtopresentthesummarytalkon
Cosmol-ogy and Gravitation. I thank George Matsas for
dis-ussionandforhelpingmeonthesubjetlassiation
of the several works presented. I also thankMaurio
Calv~aoforsuggestionsandforreadingthemanusript.
Referenes
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[6℄ M.Makler,T.Kodama,M.O.Calv~ao,astro-ph/0101113
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[12℄ M.D. Maia, E.M. Monte, preprint Universidade de
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