Can the imaginary part of permeability be negative?

Can the imaginary part of permeability be negative?

When new composite optical materials are developed experimentally or studied in numerical simulations, it is essential to have a set of fundamental constraints that the optical constants of such materials must satisfy. In this paper I argue that positivity of the imaginary part of the magnetic permeability may not be one of such constraints, particularly in naturally occurring diamagnetics and ...

How Outlandish Can Imaginary Cases Be?

It is common in moral philosophy to test the validity of moral principles by proposing counter-examples in the form of cases where the application of the principle does not give the conclusion we intuitively find valid. These cases are often imaginary and sometimes rather ‘outlandish’, involving ray guns, non-existent creatures, etc. I discuss whether we can test moral principles with the help ...

The square of the Weyl tensor can be negative

We show that the square of the Weyl tensor can be negative by giving an example: ds 2 = −dt 2 + 2yzdtdx + dx 2 + dy 2 + dz 2. This metric has the property that in a neighbourhood of the origin, C ijkl C ijkl < 0 .

Quality of life can be part of the cure.

Knowing Afghanistan: Can there be an end to the saga?

War on terrorism, as the motto which formed the cornerstone of global policies of former     neo-conservative administration of the United States, is increasingly becoming ineffective in Afghanistan with the dreaded consequence of spilling over into Pakistan. This inevitable consequence of War on    Terrorism in Afghanistan has brought the West face to face with the ‘nest of terrorism’ that CIA...