Contents - Max-Planck-Institut für Physik komplexer Systeme
Contents - Max-Planck-Institut für Physik komplexer Systeme
Contents - Max-Planck-Institut für Physik komplexer Systeme
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Forthismeeting,wedecidedtochoosetwospecificareasfortopicalsessionsanddiscussionpanels:<br />
URu2Si2andDMFT.TheenigmatichiddenorderstateinURu2Si2generateslotofinterestinthe<br />
community,withseveralnovelresultsinboththeoryandexperimentpresentedduringthelasttwoyears.<br />
Thesixtopicaltalksandadiscussionpanelwereverywellattended,andthediscussioncanbecounted<br />
asoneofthemostheateddebatesinthefield.<br />
Fromthescientificpointofview, outofover30orsotheoriesattemptingtodescribethehidden<br />
orderphase, twoseemtobesurfacing. Onetheoryapproachestheorderparameterquestionfrom<br />
thepointofviewofthefluctuationinducedlatticesymmetrybreaking,leadingtowelldevelopedand<br />
stronglyk-dependentgappingoftheFermisurface. Inthisapproach,time-reversalsymmetryisbroken<br />
onatimescalecomparabletothefluctuationstime. Theother,DMFT-basedapproach,describesthe<br />
formationofmultipolarorderintheHOphase,whichbyitselfdoesnotinvoketime-reversalsymmetry<br />
breaking. Asaresultofthisdiscussionitbecameclearthatacarefulnewexperimentconfirmingor<br />
excludingtime-reversalsymmetrybreakingwouldhelpconfirmoneofthemodels.<br />
ThesecondpaneloffourtalksanddiscussionsessionwasdevotedtotheaspectsofDynamicalMean<br />
FieldTheory(DMFT).ThediscussionshowedthatseveralapproachestoDMFTfromdifferentgroups<br />
arenotalwaysparallel,andimportantdetailslikeforexamplethetreatmentofRKKYinteraction,require<br />
furtherclarification. Nevertheless,DMFTremainstherapidlygrowingapproachtocalculatingmanybodyeffectsinf-electronsystems.<br />
Ithastobenotedthatthescientificcoordinatorsareunivocalin<br />
admirationforimpeccableorganizationoftheeventprovidedby mpipks. Theinstituteisconsiderably<br />
helpingthephysicscommunity.Mrs.Lantschwhowasinchargefortheworkshopdidanadmirablejob.<br />
We would like to build on this success and we are contemplating the possibility of organizing the<br />
focusedf-electronphotoemissionworkshopinDresden.Thereisalotofnewinformationcomingupin<br />
ARPESandincalculations,andthefieldisevolvingrapidly.Itwouldbeexcellenttocapturethisenergy<br />
andhavemostoftheplayersinthefieldmeetinoneplaceforanexcitingexchangeofinformation.<br />
WecannotthinkofabetterplacethanMPI-Dresdentohavethisevent,perhapsintheearlyFallof2012.<br />
ParticulateMatter:DoesDimensionalityMatter?,Workshop<br />
Scientificcoordinators:P.Charbonneau,K.Daniels,M.Schröter<br />
FromMay30-June4,morethan60chemists,engineers,mathematicians,andphysicistsfrom5continents<br />
gatheredforaworkshopatthe mpipkstoaddressthequestion“ParticulateMatter:DoesDimensionality<br />
Matter?” Themainfocusoftheconferencewastobetterunderstandindustrially-importantmaterials,<br />
suchassand,glasses,colloids,foams,andemulsionsbycomparingtheirbehavior–andthatofrelated<br />
models–in2,3,andmoredimensions.Lookingattheworldfromadimensionallenshelped19thcentury<br />
Flatlandreadersgraspthemetaphoricalroleofthefourthdimension;higherdimensionscanalsohelp<br />
scientistsshinenewlightonourrelativelylow-dimensionalworld.Aflatlayerofcoinspushedtogetheron<br />
atabletopandapileoforangesonagrocer’sstandhavebothsimilaritiesanddifferences.Theyareboth<br />
thedensestpossiblepackingofspheresintheirrespectivedimensions,butthewayinwhichtheyform,<br />
supportstress,andrearrange,aredifferent.Computersallowustocontrastsimilarsystemsinevenhigher<br />
dimensions. Thescientificdiscussionwaslively: notallparticipantsagreedabouttheroleofdisorder<br />
andrandomness,oreventheimportanceofthenumberofdimensions. Yet,certainlinesofagreement<br />
havestartedtoappear,aswellaskeyregimesinwhichtoconductfutureinvestigations. Theoriginal<br />
motivatingscientificquestionwasraisedtoahigherlevelthantheorganizershadanticipated. Anew<br />
awarenessofwheretolookforsimilaritiesanddifferencesindimensionalityhasarisen.Forexample,Corey<br />
O’Hernprovidedaprovocativelistof16dimension-independentpropertiesofdenseparticulatematter.<br />
Friction,polydispersity,temperature,andparticleshapearealsoimportantvariables,butisolatingthe<br />
possibleimpactofdimensionalityfromtheseotherfactorsisnecessaryifonehopestomakesenseof<br />
theresults. Aparticularemphasisonthedynamicsandstructureofdisorderedsystemswasnoted. On<br />
theonehand,theroleofdimensionalityintheoriesofjammingandtheglasstransitionledtoanimated<br />
discussionsaboutthephysicalbasisandrangeofvalidityofthemanyanalyticalapproachesexploredby<br />
variousgroups. Thestateofthequestionandthenatureofthechallengesaheadhavebecomeclearer<br />
asaresult. Ontheotherhand,thedescriptionoforderandgeometryindisorderedsystemsusing<br />
localparametersthatareaccessibleinbothsimulationsandexperiments–andaneedtounderstand<br />
howthesedifferentmeasuresdifferfromeachother–allowedtheidentificationofparallelchallenges<br />
inseparatescientificcommunities. Severalparticipatinggroupscurrentlyinaracetofindthedensest<br />
possiblepackingoftetrahedrawerepresent. Record-holderSharonGlotzergavealivelypresentation<br />
134 DetailsandData