Approximations and Mittag-Leffler conditions the tools
Identifikátory výsledku
Kód výsledku v IS VaVaI
<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216208%3A11320%2F18%3A10383321" target="_blank" >RIV/00216208:11320/18:10383321 - isvavai.cz</a>
Výsledek na webu
<a href="https://doi.org/10.1007/s11856-018-1710-4" target="_blank" >https://doi.org/10.1007/s11856-018-1710-4</a>
DOI - Digital Object Identifier
<a href="http://dx.doi.org/10.1007/s11856-018-1710-4" target="_blank" >10.1007/s11856-018-1710-4</a>
Alternativní jazyky
Jazyk výsledku
angličtina
Název v původním jazyce
Approximations and Mittag-Leffler conditions the tools
Popis výsledku v původním jazyce
Mittag-Leffler modules occur naturally in algebra, algebraic geometry, and model theory, [20], [14], [19]. If R is a non-right perfect ring, then it is known that in contrast with the classes of all projective and flat modules, the class of all flat Mittag-Leffler modules is not deconstructible [16], and it does not provide for approximations when R has cardinality ae<currency> a"mu(0), [8]. We remove the cardinality restriction on R in the latter result. We also prove an extension of the Countable Telescope Conjecture [23]: a cotorsion pair (A, B) is of countable type whenever the class B is closed under direct limits. In order to prove these results, we develop new general tools combining relative Mittag-Leffler conditions with set-theoretic homological algebra. They make it possible to trace the above facts to their ultimate, countable, origins in the properties of Bass modules. These tools have already found a number of applications: e.g., they yield a positive answer to Enochs' problem on module approximations for classes of modules associated with tilting [4], and enable investigation of new classes of flat modules occurring in algebraic geometry [26]. Finally, the ideas from Section 3 have led to the solution of a long-standing problem due to Auslander on the existence of right almost split maps [22].
Název v anglickém jazyce
Approximations and Mittag-Leffler conditions the tools
Popis výsledku anglicky
Mittag-Leffler modules occur naturally in algebra, algebraic geometry, and model theory, [20], [14], [19]. If R is a non-right perfect ring, then it is known that in contrast with the classes of all projective and flat modules, the class of all flat Mittag-Leffler modules is not deconstructible [16], and it does not provide for approximations when R has cardinality ae<currency> a"mu(0), [8]. We remove the cardinality restriction on R in the latter result. We also prove an extension of the Countable Telescope Conjecture [23]: a cotorsion pair (A, B) is of countable type whenever the class B is closed under direct limits. In order to prove these results, we develop new general tools combining relative Mittag-Leffler conditions with set-theoretic homological algebra. They make it possible to trace the above facts to their ultimate, countable, origins in the properties of Bass modules. These tools have already found a number of applications: e.g., they yield a positive answer to Enochs' problem on module approximations for classes of modules associated with tilting [4], and enable investigation of new classes of flat modules occurring in algebraic geometry [26]. Finally, the ideas from Section 3 have led to the solution of a long-standing problem due to Auslander on the existence of right almost split maps [22].
Klasifikace
Druh
J<sub>imp</sub> - Článek v periodiku v databázi Web of Science
CEP obor
—
OECD FORD obor
10101 - Pure mathematics
Návaznosti výsledku
Projekt
<a href="/cs/project/GA14-15479S" target="_blank" >GA14-15479S: Teorie reprezentací (strukturní rozklady a jejich meze)</a><br>
Návaznosti
P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)
Ostatní
Rok uplatnění
2018
Kód důvěrnosti údajů
S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů
Údaje specifické pro druh výsledku
Název periodika
Israel Journal of Mathematics
ISSN
0021-2172
e-ISSN
—
Svazek periodika
226
Číslo periodika v rámci svazku
2
Stát vydavatele periodika
IL - Stát Izrael
Počet stran výsledku
20
Strana od-do
737-756
Kód UT WoS článku
000437012800007
EID výsledku v databázi Scopus
2-s2.0-85048263134