Maybe hazard?

[Charlie84]

Hi... I have some problem with waveform in modelsim.
Consider this simple imaginary process which coresponds to process i am simulating:

process (a, b, c)
begin
output <= '0';
   if(a = '1' and b = '1' and c = '1') then
          output <= '1';
   end if;
end process;

freeimagehosting.net/image.php?356615f9b9.gif (waveform picture)

In simulation (modelsim) occur some little pulses like on the picture. Signals a, b, c comes from different logic. Signal a comes from register, b from distributed memory and c is from combinational logic. Shall I worry about the pulses? Or synthetizer (webpack) recognizes these hazards and solves it for me?