No.
Objects in assignment statements are immutable. R will copy the object not just the reference.
> v = matrix(1:12, nrow=4)
> v
[,1] [,2] [,3]
[1,] 1 5 9
[2,] 2 6 10
[3,] 3 7 11
[4,] 4 8 12
> v1 = v
> v1[,1] # fetch the first column
[1] 1 2 3 4
(proviso: the statement above is true for R primitives, e.g., vectors, matrices), and also for functions; I cannot say for certain whether it’s true for all R objects–just most of them, as well as the vast majority of the ones most often used.)
If you don’t like this behavior you can opt out of it with the help from an R Package. E.g., there is an R Package called R.oo that allows you to mimic pass-by-reference behavior; R.oo is available on CRAN.