What can be three arguments to support the theme of incest in Hamlet?Hamlet by William Shakespeare

A third argument made is that Hamlet has an Oedipal
complex about his mother.  This psychological disorder determined by Sigmund Freud
involves the unconscious desire of a son to kill his father and take his place as the
object of his mother's love.  According to Ernest Jones, critic, in his article, "The
Psycho-Analytical Solution," Hamlet tarries in his seeking revenge on Claudius because
he shares Claudius's guilt in desiring Gertrude.  Therefore, his inaction is a result of
his "tortured conscience" and his melancholy is caused by his "repressed feelings." 
Jones further maintains that driven by the "unconscious" part of his mind, Hamlet is
painfully thrawted.  And, his "indignation" at his father's murder is superceded by his
"intensest horror" at his mother's incestual relation with
Claudius.

That Hamlet may have the Oedipal complex is
evidenced, critics say, in his soliloquy against Gertrude in Act
I

....She
married.  O, most wicked speed, to post

With such dexterity
to incestuous sheets!
(1.2.155-156)

and, especially
when he rails against her like a jealous lover in Act
III:

...You
cannot call it love, for at your age

The heyday in the
blood is tame, it's humble....

What devil
ws't

That thus hath cozened you at
hoodman-blind?

Eyes without feeling, feeling without
sight...

...O shame, where is thy
blush?

Rebellious hell,

If
thou canst mutine in a matron's bones,

To flaming youth let
virtue bea as wax

And melt in her own fire.  Proclaim no
shame

When the compulsive ardor gives the charge
(3.4.69-87)

The site below
contains the full article on Hamlet's Oedipal Complex.