عنوان مجله
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PROCEEDINGS OF THE INDIAN ACADEMY OF SCIENCES-MATHEMATICAL SCIENCES
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چکیده
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In this article, using the pullback (fiber product) of schemes we define a
natural operation, the so-called multiplication, on the set of closed subschemes of a
given scheme in an alternative way. It is well known that the pushout of any two closed
immersions of schemes with a fixed source exists in the category of schemes. This
result allows us to define a second operation, the so-called addition, on the set of closed
subschemes of a scheme. Next, it is proved that these structures naturally provide us
contravariant functors from the category of schemes to the category of commutative
monoids.
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