As the vacuum state of a quantum field is not an eigenstate of the Hamiltonian density, the vacuum energy density can be represented as a random variable. We present an analytical calculation of the probability distribution of the vacuum energy densi
ty for real and complex massless scalar fields in Minkowski space. The obtained probability distributions are broad and the vacuum expectation value of the Hamiltonian density is not fully representative of the vacuum energy density.
We present an improved QCD light-cone sum rule (LCSR) calculation of the B -> K and Bs -> K form factors, by including SU(3)-symmetry breaking corrections. We use recently updated K-meson distribution amplitudes which incorporate the complete SU(3)-b
reaking structure. By applying the method of the direct integration in the complex plane, which is presented in a detail, the analytical extraction of the imaginary parts of LCSR hard-scattering amplitudes becomes unnecessary and therefore the complexity of the calculation is greatly reduced. The values obtained for the relevant B_{(s)} -> K form factors are as follows: f^+_{BK}(0)= 0.36^{+0.05}_{-0.04}, f^+_{B_sK}(0)= 0.30^{+0.04}_{-0.03} and f^T_{BK}(0)= 0.38pm 0.05, f^T_{B_sK}(0)= 0.30pm 0.05. By comparing with the B -> pi form factors extracted recently by the same method, we find the following SU(3) violation among the B -> light form factors: f^+_{BK}(0)/f^+_{Bpi}(0) = 1.38^{+0.11}_{-0.10}, f^+_{B_sK}(0)/f^+_{Bpi}(0) = 1.15^{+0.17}_{-0.09}, f^T_{BK}(0)/f^T_{Bpi}(0) = 1.49^{+0.18}_{-0.06} and f^T_{B_sK}(0)/f^T_{Bpi}(0) = 1.17^{+0.15}_{-0.11}.
