Is there a way to not display the sign on page in appian?

Kaushik,
LDAP authentication does not provide SSO capability. The mobile application works without a login page because the credentials are stored on the device and supplied with each request going through your LDAP authentication. The Cloud team can setup SSO for your site (forum.appian.com/.../SAML_with_Appian_Cloud) but it currently is not compatible with mobile devices.

I think you can comment out the login page within the spring override file and it should work.