Are ghosts real? Or are they made possible through a slight of physics?

I've been watching shows like The Dresden Files (which by the way was an AWESOME show on Scifi--too bad they cancelled it!), Ghost Whisperer, Sliders, and a host of other shows, and it dawned on me that we think of things in terms of what we understand--is it true that we can sense and feel things that are other worldy? Can the dead really be able to visit us on this plane of existence, via some metaphysical form, like the Slimer from Ghostbusters or some whispy ghostly manifestation?

After watching Sliders (actually that's not true, I'm still waiting it and only through season 2), but the concept that is behind the show, being able to go between the EPR plane and literally slide between parallel dimensions, struck me as strange but at the same time kind of thought provoking. What if, at the present moment we can't slide between dimensions, but what if there are tiny holes that can exist between dimensions, weak spots if you will, and it is in those intersection points that we find it possible to "view" individuals from one dimension to another. What if, the reason some people can "talk" to those who have pasted, is that in this particular house at this particular location at this particular time and space, the tear has allowed for a window into a dimension where that individual is very much alive? Is it so fantastic to think that this is possible? Wouldn't that go volumes to try and explain much of what we see around us that we don't know, but on the other side, is rather terrifying in the idea that there can be tears between dimensions or time and space for that matter. We think of time and space in a more fluid or undistrubed plane of existence, but what if that plane is rifed with pot-holes or various other dimples that cause discontinuity between what we would consider to be normal and what is not normal.