let r be an associative ring with identity, c(r) be the category of com-plexes of r-modules and flat(c(r)) be the class of all at complexes of r-modules. we show that the at cotorsion theory (flat(c(r)); flat(c(r))−)have enough injectives in c(r). as an application, we prove that for each atcomplex f and each complex y of r-modules, exti (f,x)= 0, whenever ris n-perfect and i > n.

For an (n − 1)-Auslander algebra Λ with global dimension n ≥ 2, we show that if Λ admits a trivial maximal (n − 1)-orthogonal subcategory of modΛ, then Λ is of finite representation type and the projective dimension or injective dimension of any indecomposable module in modΛ is at most n − 1. As a result, we have that for an Auslander algebra Λ with global dimension 2, if Λ admits a trivial max...

In a 2013 paper, Cheeger and Kleiner introduced new type of dimension for metric spaces, the “Lipschitz dimension”. We study dimension-theoretic properties Lipschitz dimension, including its behavior under Gromov–Hausdorff convergence, (non-)

introduction nowadays, many studies were performed about noise source and its type and effects related to duration of sound emission. most of these researches just report sound pressure level in frequency or time domain. these researches should be continued in order to find better absorber material in noise pollution. use of fractal geometry is a new method in this filed. wave fractal dimension...

0. Introduction 1 1. General properties of the cohomological dimension 2 2. Bockstein theory 6 3. Cohomological dimension of Cartesian product 10 4. Dimension type algebra 15 5. Realization theorem 19 6. Test spaces 24 7. Infinite-dimensional compacta of finite cohomological dimension 28 8. Resolution theorems 33 9. Resolutions preserving cohomological dimensions 41 10. Imbedding and approximat...