is it a bug in mvc4 on cross domain authentication? - asp.net-mvc-4

Question

i used cross domain cookie authentication on mvc3 and .net4 it works fine and nice,
i create a another project on mvc4 and .net 4.5 and copy/past my codes from lower to uper version on mvc (i mean to mvc4),now my authentication cookie create on main domain but sub domain can not realize that user has been authenticated.
is it a bug in mvc4 or i must enable some futures or somethings like this?
my codes to create authentication cookie on main domain:
FormsAuthenticationTicket ticket = new FormsAuthenticationTicket(
1,
"fc5f06b006b44b05a257c406f4218638",//username
DateTime.Now,
DateTime.Now.AddDays(5),
true,
"members",
FormsAuthentication.FormsCookiePath);
// To give more security it is suggested to hash it
string hashCookies = FormsAuthentication.Encrypt(ticket);
HttpCookie cookie = new HttpCookie(FormsAuthentication.FormsCookieName,
hashCookies); // Hashed ticket
cookie.Expires = DateTime.Now.AddDays(5);
cookie.Domain = ".maindomain.com";
Response.Cookies.Add(cookie);
in sub domain use this line of codes to test user authentication:
var result = System.Web.HttpContext.Current.User.Identity.IsAuthenticated + "-" +
System.Web.HttpContext.Current.User.Identity.Name;
and in my global i have:
protected void Application_AuthenticateRequest(object sender, EventArgs e)
{
// look if any security information exists for this request
if (System.Web.HttpContext.Current.User != null)
{
// see if this user is authenticated, any authenticated cookie (ticket) exists for this user
if (HttpContext.Current.User.Identity.IsAuthenticated)
{
// see if the authentication is done using FormsAuthentication
if (System.Web.HttpContext.Current.User.Identity is FormsIdentity)
{
// Get the roles stored for this request from the ticket
// get the identity of the user
FormsIdentity identity = (FormsIdentity)System.Web.HttpContext.Current.User.Identity;
// get the forms authetication ticket of the user
FormsAuthenticationTicket ticket = identity.Ticket;
// get the roles stored as UserData into the ticket
string[] roles = ticket.UserData.Split(',');
// create generic principal and assign it to the current request
System.Web.HttpContext.Current.User = new System.Security.Principal.GenericPrincipal(identity, roles);
}
}
}
}
and in my web config :
<authentication mode="Forms">
<forms domain=".maindomain.com" name="atnc"
loginUrl="~/home" timeout="120" requireSSL="false" />
</authentication>