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The R.A.P. Project (Reviews of Astro-Ph) 2003

Chislennoe modelirovanie
(Arhiv Chislennoe modelirovanie:
v.2, 2004, v.1, 2002-2003)

Vypusk 63. 16-31 dekabrya 2003

astro-ph/0312651 Sravnenie programm kosmologicheskogo modelirovaniya AMR i SPH (Comparing AMR and SPH Cosmological Simulations: I. Dark Matter & Adiabatic Simulations)
Authors: Brian W. O'Shea et al.
Comments: 35 pages, 18 figures. Submitted to the Astrophysical Journal

Chislennoe modelirovanie - vazhneishii instrument v kosmologicheskih issledovaniyah. Sushestvuet mnogo razlichnyh podhodov k "sozdaniyu vselennoi v probirke". Sootvetstvenno, neobhodimo sravnivat' raznye podhody monopolizm i otsutstvie svobodnogo kompetentnogo obsuzhdeniya nauke protivopokazano).

Avtory (izvestneishie specialisty v svoei oblasti) sravnivayut dva chislennyh koda, osnovannyh na raznyh metodikah. Obsuzhdayutsya prichiny neskol'ko razlichayushihsya rezul'tatov raboty dvuh programm.


Vypusk 59. 19-31 oktyabrya 2003

miniobzor astro-ph/0310702 GRAPE-6: special'nyi parallel'ni komp'yuter dlya astrofizicheskogo modelirovaniya (GRAPE-6: The massively-parallel special-purpose computer for astrophysical particle simulation)
Authors: Junichiro Makino et al.
Comments: 25 pages, Accepted for publication in PASJ, scheduled to appear in Vol.55, No. 6

Daetsya obzor novoi versii parallel'nyh superkomp'yuterov serii GRAPE (GRAvity piPE) dlya modelirovaniya metodom mnogih tel, aktivno primenyayushimsya v astrofizike (struktura i vzaimodeistvie galaktik, zvezdnye skopleniya, krupnomasshtabnaya struktura, ustoichivost' i formirovanie planetnyh sistem i t.p.). Seriya nachalas' v nachale 90-h godov i, razumeetsya, moshnost' komp'yuterov bystro rosla. Komp'yutery GRAPE-3 i -5 proizvodilis' dazhe malymi seriyami, chto pozvolilo sdelat' ih ne ochen' dorogimi (t.e. dostupnymi bol'shinstvu krupnyh universitetov, gde byli sootvetstvuyushie gruppy issledovatelei). GRAPE-6 imeet 2048 processorov. Maksimal'naya skorost' - 64 Teraflopa.

Stat'ya budet bezuslovno interesna vsem, kto interesuetsya chislennymi metodami, komp'yuternym modelirovanie i t.p.


astro-ph/0310734 Biblioteka sliyanii galaktik (A library of galaxy mergers)
Authors: F. Combes, A.-L. Melchior
Comments: 2 pages, 2 figures, contribution in Scientific Highlights, SF2A-2003, to be published by EDP-Sciences

Korotkii otchet o hode rabot nad interesnym proektom. Avotry postavili svoei zadachei s pomosh'yu chislennogo modelirovaniya poluchit' biblioteku slivayushihsya galaktik. Kak horosho izvestno, vzaimodeistvie galaktik mozhet porozhdat' ves'ma prichudlivye konfiguracii. Bylo by interesno zaranee imet' nabor simulyacii. Dlya togo, chtoby eto davalo otdachu, nuzhno imet' okolo 1000 smodelirovannyh sliyanii. Bol'shaya rabota!


astro-ph/0310786 FLY. Parallel'nyi drevesnyi kod dlya kosmologicheskogo modelirovaniya. Rukovodstvo po primeneniyu (FLY. A parallel tree N-body code for cosmological simulations. Reference Guide)
Authors: V. Antonuccio-Delogu, U. Becciani, D. Ferro
Comments: 29 pages, 4 figures. Code included in CPC program library Catalogue identifier: ADSC. Comput. Phys. Commun. 155(2003)159

Sushestvuet dostatochno mnogo otkrytyh kodov dlya samyh razlichnyh celei. V tom chisle i dlya kosmologicheskogo modelirovaniya. V dannoi stat'e avtory predstavlyayut opisanie programmy FLY. Rabota, razumeetsya, ochen' tehnicheskaya, no budet interesna tem, kto interesuetsya chislennym modelirovaniem.


astro-ph/0310789 Magnitogidrodinamika sglazhennyh chastic (Smoothed Particle Magnetohydrodynamics I. Algorithms and tests in one dimension)
Authors: D.J. Price, J.J. Monaghan
Comments: 16 pages, 7 figures, accepted to MNRAS

Dve stat'i (vtoraya "Smoothed Particle Magnetohydrodynamics II. Variational principles and variable smoothing length terms"), posvyashennye modelirovaniyu metodom sglazhennyh chastic (Smoothed Particle Hydrodynamics (SPH)).

Predlozhen novyi algoritm, kotoryi proveren mnozhestvom odnomernyh testov, predstavlennymi v etih dvuh rabotah. Predpolagaetsya, chto algoritm budet kraine polezen v astrofizicheskih prilozheniyah (vklyuchaya neideal'nuyu MGD).


dissertaciya gr-qc/0310116 Chislennoe issledovanie relyativistskogo kollapsa (A Numerical Study of Relativistic Fluid Collapse)
Authors: Scott C. Noble
Comments: 228 pages, 66 Postscript figures, Ph.D. Thesis, the University of Texas at Austin, uses utdiss2.sty v5

Dissertaciya posvyashena chislennomu modelirovaniya gravitacionnogo kollapsa. Tema arhislozhnaya i arhiaktual'naya.


Vypusk 57. 22-30 sentyabrya

astro-ph/0309539 Kollaps yader v treh izmereniyah (3-Dimensional Core-Collapse)
Authors: C. L. Fryer and M. S. Warren
Comments: 34 pages (5 of 17 figures missing), accepted by ApJ

Eta stat'ya - prazdnik trehmernyh raschetov, kotorye byli vypolneny dlya serii modelei s razlichnoi skorost'yu vrasheniya i magnitnym polem. Samoe bystroe iz rassmotrennyh vrashenii ne privodit k fragmentacii zvezdy i ne vyzyvaet sushestvennyh izmenenii v processah konvekcii v centre ee yadra. Analogichno, rassmatrivalis' ne slishkom sil'nye magnitnye polya, kotorye ne dominiruyut v processe vzryva sverhnovoi (bolee sil'nye magnitnye polya, nablyudaemye u neitronnyh zvezd, mogut voznikat' pri ih posleduyushem ohlazhdenii i szhatii). V modeli s samym bystrym vrasheniem mozhet obrazovat'sya pul'sar, energii vrasheniya kotorogo budet dostatochno dlya sbrosa obolochki sverhnovoi. No sovremennye evolyucionnye teorii predskazyvayut slishkom medlennoe vrashenie u predsverhnovyh, chtoby takoi (magnitorotacionnyi) mehanizm mog srabotat'.


math.NA/0309285 Algoritm optimal'nogo deleniya dannyh na intervaly (An Algorithm for Optimal Partitioning of Data on an Interval)
Authors: Brad Jackson et al.
Comments: 4 pages, 1 figure, submitted to IEEE Signal Processing Letters

Pravil'no razdelit' nablyudatel'nye dannye na intervaly, chtoby zatem ih udachno approksimirovat' - pochti iskusstvo. V dannoi zametke opisan prostoi, no moshnyi algoritm, kotoryi prosmatrivaet vse vozmozhnye varianty razbieniya N tochek dannyh za vremya poryadka N2 (obrashaem vnimanie, chto obshee chislo variantov razbieniya proporcional'no eN). Algoritm garantirovanno nahodit global'nyi optimum i avtomaticheski opredelyaet chislo intervalov na kotoroe nado razbit' ishodnye dannye. Algoritm legko obobshaetsya na mnogomernye dannye. Vozmozhna, takzhe, ego rabota v real'nom vremeni.


Primer razbieniya nabora dannyh na intervaly


astro-ph/0309565 Ochistka baz dannyh obzorov neba novymi metodami (Cleaning sky survey databases using Hough Transform and Renewal String approaches)
Authors: A.J. Storkey et al.
Comments: 17 pages, Accepted for MNRAS.

Bazy dannyh bol'shih obzorov neba (naprimer, SuperCOSMOS Sky Survey, SSS), takzhe kak i otdel'nye nablyudeniya, "zasoryayutsya" proletami iskusstvennyh sputnikov i samoletov, fizicheskimi defektami priemnikov (segodnya eto, v osnovnom, PZS) i t.d. Odnako, esli poyavlenie podobnyh defektov v odinochnyh nablyudeniyah mozhno obnaruzhit' i, po vozmozhnosti, ustranit' v ruchnuyu, to v avtomaticheski provodimyh obzorah bol'shogo ob'ema takoe reshenie nevozmozhno.

Dannaya stat'ya posvyashena obnaruzheniyu i udaleniyu iz dannyh obzorov "trekov" iskusstvennyh sputnikov zemli i samoletov i drugih lineinyh defektov.

Polnuyu versiyu stat'i (s risunkami) mozhno vzyat' na saite avtorov http://www.anc.ed.ac.uk/~amos/publications.html, a detali proekta uznat' zdes'.


Vypusk 56. 13-20 sentyabrya 2003

astro-ph/0309388 "Zolotye kopi": novaya baza dannyh galaktik v web (GOLD Mine: A new Galaxy Database on the WEB)
Authors: G.Gavazzi et al.

Baza dannyh o galaktikah "GOLDmine" ("Zolotye kopi") byla sushestvenno obnovlena k sentyabryu 2003 g. Adres bazy dannyh: http://goldmine.mib.infn.it/.


astro-ph/0309395 MODEST: modelirovanie zvezdnoi evolyucii i (gidro)dinamiki (MODEST: modeling stellar evolution and (hydro)dynamic)
Authors: Piet Hut
Comments:4 pages, review talk presented at JD-11, IAU General Assembly XXV, Sydney, July 2003, to be included in Highlights of Astronomy, Vol. 13

Skromnoe nazvanie sistemy MODEST ne dolzhno vvodit' v zabluzhdenie. Eto krupnyi proekt, kotoryi daet vozmozhnost' provodit' kompleksnoe modelirovanie plotnyh zvezdnyh sistem, naprimer, sharovyh skoplenii. Nekotorye kuski koda dostupny v Internet. Proekt ob'edinyaet neskol'ko issledovatel'skih grupp po vsemu miru. V stat'e daetsya obzor pervogo goda raboty.


Vypusk 51. 21-31 iyulya 2003

cs.NA/0307033 Velikolepie v komp'yuternom modelirovanii (Excellence in Computer Simulation)
Authors: Leo P. Kadanoff
Comments: 30 pages, 8 figures

Avtor stat'i rabotaet v Department of Energy (chto-to tipa nashego MinSredMasha) uzhe davno. Yasno, chto imenno takie vedomstva imeyut vozmozhnost' provodit' ochen' slozhnye chislennye eksperimenty.

Stat'ya ochen' i ochen' interesnaya. Vsem sovetuem prochest'. Opisano mnogo konkretnyh rabot (osobenno v oblasti izucheniya povedeniya haoticheskih sistem).

Interesno, "a kak u nas?".....

obzor astro-ph/0307400 Modelirovanie spiral'nyh struktur v relyativistskih struyah (Modeling Helical Structures in Relativistic Jets)
Authors: P.E. Hardee
Comments: 18 pages, 7 figures

Bol'shoe kolichestvo astronomicheskih ob'ektov vybrasyvaet strui (ili, kak ih eshe nazyvayut, dzhety). Eto i obrazuyushiesya zvezdy, i kompaktnye ob'ekty v tesnyh dvoinyh sistemah, i sverhmassivnye chernye dyry v yadrah galaktik.... Esli skorost' dzheta velika, to ih nazyvayut relyativistskimi, t.k. nuzhno uchityvat' effekty special'noi teorii otnositel'nosti. Krome togo, vo mnogih dzhetah nablyudayut zakruchennye (spiral'nye) struktury. Ob'yasneniyu etogo fenomena, a takzhe popytkam vosproizvesti podobnye struktury v chislennyh eksperimentah, posvyashena dannaya rabota.


Vypusk 48. 23-30 iyunya 2003


astro-ph/0306418 Raschet sliyaniya neitronnyh zvezd s vysokim razresheniem III: gamma-vspleski (High Resolution Calculations of Merging Neutron Stars III: Gamma-Ray Bursts)
Authors: S.Rosswog, E.Ramirez-Ruiz, M.B.Davies
Comments: 23 pages, 13 figures, submitted to MNRAS

Eto ne pervyi raschet sliyaniya dvoinoi neitronnoi zvezdy (i uzh tem bolee ne poslednii). Osnovnaya problema zdes' sostoit v sleduyushem provodit' etot raschet mozhno tol'ko v treh izmereniyah (poskol'ku zadacha ne obladaet osevoi simmetriei), a esli, kak v dannom sluchae, uchityvayutsya magnitnye polya, to trebovaniya k ob'emam komp'yuternoi pamyati stanovyatsya ochen' bol'shimi. Bol'shinstvo predydushih raschetov velos' na malyh setkah (s nizkim razresheniem), imenno poetomu kazhdoe sushestvennoe uvelichenie razresheniya v takih raschetah vyzyvaet bol'shoi interes.

Chislennym raschetam sliyaniya dvoinyh neitronnyh zvezd i izluchayushihsya pri etom gravitacionnyh voln posvyashen takzhe preprint astro-ph/0306481 k kotoromu prilagaetsya fil'm.

Vypusk 45. 26-31 maya 2003

astro-ph/0305475 Ocenka effekta "Bych'ego Glaza" (Quantifying the Bull's Eye Effect)
Authors: B.C.Thomas, A.L.Melott, H.A.Feldman, S.F.Shandarin
Comments: 21 pages, 5 figures, 3 tables; submitted to ApJ

V etoi stat'e rassmatrivaetsya i kolichestvenno ocenivaetsya, s pomosh'yu chislennogo modelirovaniya metodom N-tel, nablyudayushiisya vklad dvuh effektov s ochen' poeticheskimi nazvaniyami "Pal'cy Boga" (Fingers of God) i "effekt Bych'ego Glaza" (Bull's Eye Effect). Oba etih effekta svyazany s otkloneniyami dvizhenii otdel'nyh ob'ektov (galaktik) ot zakona Habbla. Eti otkloneniya svyazany s tem, chto krome uchastiya v obshem Habblovskom rasshirenii imeyut sobstvennye pekulyarnye skorosti (otnositel'no dvizheniya Habblovskogo potoka v srednem).

Pervyi effekt svyazan s dvizheniyami galaktik v kompaktnyh stacionarnyh skopleniyah. Virial'nye skorosti ob'ektov tam dostigayut tysyach kilometrov v sekundu, polovina galaktik dvizhetsya k nam (ih krasnoe smeshenie z umen'shaetsya), vtoraya polovina - ot nac (z stanovitsya bol'she). Togda pri postroenii trehmernogo raspredeleniya ob'ektov, kogda rasstoyanie vychislyaetsya cherez luchevuyu skorost' (krasnoe smeshenie) po zakonu Habbla, v napravlenii virializovannyh skoplenii my uvidim vytyanutye vdol' lucha zreniya "sigary" - "'Pal'cy Boga' so vseh storon ukazyvayushie na nas".

Vtoroi effekt ("effekt Bych'ego Glaza") rabotaet na bol'shih masshtabah i deistvuet v protivopolozhnuyu storonu (t.e. ne rastyagivaet, a szhimaet raspredelenie ob'ektov po z). On deistvuet v bolee krupnyh strukturah (skopleniyah i sverh skopleniyah), kotorye ne dostigli stacionarnogo sostoyaniya i vse eshe prodolzhayut kollapsirovat'. V etom sluchae ob'ekty raspolozhennye na blizhnei k nas storone takogo ob'ekta udalyayutsya ot nas v srednem bystree, chem po zakonu Habbla, a na dal'nei storone - v srednem medlennee. V itoge takoi ob'ekt po krasnomu smesheniyu zanimaet men'shii interval, chem sootvetstvuyushii ego geometricheskim razmeram. K sozhaleniyu, proishozhdenie nazvaniya etogo effekta ne ponyatno.


Illyustraciya vozniknoveniya effektov "Pal'cev Boga" i "Bych'ego Glaza".

Vypusk 43. 12-16 maya 2003

astro-ph/0305210 Evolyuciya fluktuacii barionnoi plotnosti v mnogokomponentnyh kosmologicheskih simulyaciyah (The Evolution of Baryon Density Fluctuations in Multi-Component Cosmological Simulations)
Authors: Naoki Yoshida et al.
Comments: submitted to MNRAS

Metody raschetov nuzhno postoyanno uluchshat'. V stat'e avtory obsuzhdayut problemu postanovki pravil'nyh nachal'nyh uslovii pri modelirovanii v kosmologii. Delo v tom, chto struktura poyavlyaetsya iz uzhe sushestvovavshih fluktuacii plotnosti. Vazhno pravil'no ih zadat'. Avtory delayut neskol'ko "progonov" s raznymi parametrami, i dayut svoi rekomendacii po vyboru nachal'nyh uslovii i rabote s nimi.


(Arhiv Chislennoe modelirovanie:
v.2, 2004, v.1, 2002-2003)

Publikacii s klyuchevymi slovami: astrofizika - obzory - astro-ph
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