Discussion of Homotopy Type Theory and Univalent Foundations
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* [HoTT] Question regarding terminology regarding injectivity of objects
@ 2019-02-08 21:06 Martín Hötzel Escardó
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From: Martín Hötzel Escardó @ 2019-02-08 21:06 UTC (permalink / raw)
  To: Homotopy Type Theory

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Question regarding terminology regarding injectivity of objects:

(1) An object D is called injective over an arrow j:X->Y if the 
"restriction map" 

    hom(Y,D) -> hom(X,D) 
        g   |-> g o j 

is a surjection. This is fairly standard terminology (where does it come 
from, by the way). 

(2) I am working with the situation where the restriction map is a **split** 
surjection. 

I thought of the terminology "D is split injective over j", but perhaps 
this is awkward. Is there a standard terminology for this notion. Or, 
failing that, a terminology that at least one person has already used in 
the literature or in the folklore. Or, failing that too, a good suggestion 
by any of you? 

(Before anybody says that there is no difference assuming choice, I remark 
that I am interested in the "infty-category of types (in a universe)" in 
HoTT/UF, where the homs are infty-groupoids and so the section has to be a 
morphism, not just a theoretical function.)

Thanks, 
Martin

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