Hot dark matter Dark matter

-


hot dark matter consists of particles fsl larger size of protogalaxy. neutrino qualifies such particle. discovered independently, long before hunt dark matter: postulated in 1930, , detected in 1956. neutrinos mass less 10 of electron. neutrinos interact normal matter via gravity , weak force, making them difficult detect (the weak force works on small distance, neutrino triggers weak force event if hits nucleus head-on). makes them weakly interacting light particles (wilps), opposed wimps.


the 3 known flavours of neutrinos electron, muon, , tau. masses different. neutrinos oscillate among flavours move. hard determine exact upper bound on collective average mass of 3 neutrinos (or of 3 individually). example, if average neutrino mass on 50 ev/c (less 10 of mass of electron), universe collapse. cmb data , other methods indicate average mass not exceed 0.3 ev/c. thus, observed neutrinos cannot explain dark matter.


because galaxy-size density fluctuations washed out free-streaming, hot dark matter implies first objects can form huge supercluster-size pancakes, fragment galaxies. deep-field observations show instead galaxies formed first, followed clusters , superclusters galaxies clump together.








Comments

Post a Comment

Popular posts from this blog

CACHEbox ApplianSys

-
cachebox230 server appliance cachebox s caching engine employs code squid project. in 2005 launched becta approved protex content filtering service in collaboration east of england broadband network, represent more 2800 schools across 10 authorities. in 2006, acquired assets , customer base of rival freedom2. has since expanded activity north american schools market , caching device requested schools 2015 e-rate funding.
Read more

Kinship systems Apache

-
hide painting depicting apache girl s puberty ceremony, naiche (chiricahua apache), ca. 1900, oklahoma history center the chiricahua language has 4 different words grandparent: -chú maternal grandmother , -tsúyé maternal grandfather , -chʼiné paternal grandmother , -nálé paternal grandfather . additionally, grandparent s siblings identified same word; thus, 1 s maternal grandmother, 1 s maternal grandmother s sisters, , 1 s maternal grandmother s brothers called -chú. furthermore, grandparent terms reciprocal, is, grandparent use same term refer grandchild in relationship. example, person s maternal grandmother called -chú , maternal grandmother call person -chú (i.e. -chú can mean child of either own daughter or sibling s daughter.) chiricahua cousins not distinguished siblings through kinship terms. thus, same word refer either sibling or cousin (there not separate terms parallel-cousin , cross-cousin). additionally, terms used according sex of speaker (unlike english terms broth...
Read more

Western Apache Apache

-
a western apache woman san carlos group western apache include northern tonto, southern tonto, cibecue, white mountain , san carlos groups. while these subgroups spoke same language , had kinship ties, western apaches considered separate each other, according goodwin. other writers have used term refer non-navajo apachean peoples living west of rio grande (thus failing distinguish chiricahua other apacheans). goodwin s formulation: apache peoples have lived within present boundaries of state of arizona during historic times exception of chiricahua, warm springs, , allied apache, , small band of apaches known apache mansos, lived in vicinity of tucson. cibecue western apache group, according goodwin, north of salt river between tonto , white mountain apache, consisting of ceder creek, carrizo, , cibecue (proper) bands. san carlos. western apache group ranged closest tucson according goodwin. group consisted of apache peaks, arivaipa, pinal, san carlos (proper) bands. arivaipa (also ara...
Read more