thanks Jermey! This is helpful. I was wondering, if this also means, Braque knew Delaunay?  And, I appreciate any thoughts on whether Braque knew Arp.

To give you some context for my question, I am trying to get a sense of the social world of Braque--the people he was friends with, collaborated with or had any other relationship with before or during 1910-25. I understand that Sonia Delaunay's ex-husband, Wilhelm Uhde, was Braque's dealer.  Taken together, all this might obviously indicate  that Braque knew Robert Delaunay. But I am yet to come across evidence documenting  this.  Similarly, I understand, Braque and Arp were guests of American patron Paul Nelson around 1927 at the latter's house in Varengeville. But it is not clear if this means Braque and Arp knew each other before or during 1910-25.

Duchamp knew Braque and visited him many times in atelier between 1910 and 1911 while Braque was engaged in "analyrical Cubism". Duchamp's conception of Cubism was very much influenced by Braque effort towards visual strenght and order - at that time Duchamp was much closer to Braque's idea of cubism than to Picasso's one. The writer Roché was an intimate friend of both and write about them. As for Delaunay and Arp: obviously Delaunay knew Braque in Paris during the pre-war years, the problem is if Braque was interested in Delaunay. I strongly doubt about it. Nor Braque neither Picasso had interest in "orphism" or everything but their own interpretation of cubism. As for Arp: he was a young, swiss painter before being known as a Dada artist after 1917. I don't think Braque knew anything about him before the first world war end. 

thank you Jeremy and Michele! this is very interesting. @Jeremy, your comment about artists co-exhibiting with each other (such as at the Salon des Indépendants) made me think of another question: Your comment suggests that such artists were very likely to know each other.   I think this is true in this instance specially given the common friends and also "very broad" commonality of the Cubist art movement. But is this in general that artists co-exhibiting with each knew each other? In case of the Salon des Independants, artists often coordinated with their peers to make sure  their work was exhibited in the same room as their peers.  This was possible given that the Salon des Independants was unjuried.   And also used by artists as a strategy to avoid  "getting lost" in the huge number of works. So it is likely that artists exhibiting in the same room in the Salon des Independants knew each other. but what about artists co-exhibiting exhibiting in different rooms? and what about co-exhibitions at other exhibitions such as Salon d'Automne, the Sonderbund, NKVM etc.

Double check the info about the Salon. After 1908, Braque was working with Picasso for Kahnweiler and the two artists were famous for not showing in the Salons once the dealer was on the scene. Braque collaborated with PIcasso only. If one wanted to see his work, it was necessary to go to his studio or to Kahnweiler's gallery.