Probability densities

When providing input for the STOMP calculation a range of values of porosity (and all of the other input parameters) should be provided, based on the measured data and estimates of how the parameters may vary away from the control points. The uncertainty associated with each parameter may be expressed in terms of a probability density function, and these may be combined to create a probability density function for STOMP. 

It is common practice within oil companies to use expectation curves to express ranges of uncertainty. The relationship between probability density functions and expectation curves is a simple one. 

Figure 6.6 The probability density function and the expectation curve...

To extract infomiation from the wavefimction about properties other than the probability density, additional postulates are needed. All of these rely upon the mathematical concepts of operators, eigenvalues and eigenfiinctions. An extensive discussion of these important elements of the fomialism of quantum mechanics is precluded by space limitations. For fiirther details, the reader is referred to the reading list supplied at the end of this chapter. In quantum mechanics, the classical notions of position, momentum, energy etc are replaced by mathematical operators that act upon the wavefunction to provide infomiation about the system. The third postulate relates to certain properties of these operators ... 

Figure Al.1.2. Probability density (v[/ vt/) for the n = 29 state of the hamionic oscillator. The vertical state is chosen as in figure A1.1.1. so that the locations of the turning points comcide with the superimposed potential fiinction.

The canonical distribution corresponds to the probability density for the system to be in a specific microstate with energy E- H, from it one can also obtain the probability P( ) that the system has an energy between E and E + AE i the density of states D E) is known. This is because, classically. 

I i i(q,01 in configuration space, e.g. as defined by the possible values of the position coordinates q. This motion is given by the time evolution of the wave fiinction i(q,t), defined as die projection ( q r(t)) of the time-dependent quantum state i i(t)) on configuration space. Since the quantum state is a complete description of the system, the wave packet defining the probability density can be viewed as the quantum mechanical counterpart of the classical distribution F(q- i t), p - P t)). The time dependence is obtained by solution of the time-dependent Schrodinger equation... 

Figure A3.13.6. Time evolution of the probability density of the CH cliromophore in CHF after 50 fs of irradiation with an excitation wave number = 2832.42 at an intensity 7q = 30 TW cm. The contour...

Figure A3.13.9. Probability density of a microcanonical distribution of the CH cliromophore in CHF within the multiplet with cliromophore quantum nmnber V= 6 (A. g = V+ 1 = 7). Representations in configuration space of stretching and bending (Q coordinates (see text following (equation (A3.13.62)1 and figure A3.13.10). Left-hand side typical member of the microcanonical ensemble of the multiplet with V= 6...

Figure A3.13.10. Time-dependent probability density of the isolated CH clnomophore in CHF. Initially, tlie system is in a Fenni mode with six quanta of stretching and zero of bending motion. The evolution occurs within the multiplet with chromophore quantum number A = 6 = A + 1 = 7). Representations are given...

Figure A3.13.il. Illustration of the time evolution of redueed two-dimensional probability densities I I and I I for the exeitation of CHD between 50 and 70 fs (see [154] for further details). The full eurve is a eut of tire potential energy surfaee at the momentary absorbed energy eorresponding to 3000 em during the entire time interval shown here (as6000 em, if zero point energy is ineluded). The dashed eurves show the energy uneertainty of the time-dependent wave paeket, approximately 500 em Left-hand side exeitation along the v-axis (see figure A3.13.5). The vertieal axis in the two-dimensional eontour line representations is...

The wave paeket motion of the CH eliromophore is represented by simultaneous snapshots of two-dimensional representations of the time-dependent probability density distribution... 

Figure A3.13.13. Illustration of the time evolution of redueed two-dimensional probability densities I and I I for the isolated CHD2T (left-hand side) and CHDT, (right-hand side) after 800 fs of free evolution. At time 0 fs the wave paekets eorresponded to a loeafized, ehiral moleeular stnieture (from [154]). See also text and figure A3.13.il.

Figure Bl.2.4. Lowest five hannonic oscillator wavefimctions / and probability densities i if.

Here pyy r ) represents the probability density for finding the 1 electrons at r, and e / mutual Coulomb repulsion between electron density at r and r. ... 

The magnitude and shape of such a mean-field potential is shown below [21] in figure B3.1.4 for the two 1 s electrons of a beryllium atom. The Be nucleus is at the origin, and one electron is held fixed 0.13 A from the nucleus, the maximum of the Is orbital s radial probability density. The Coulomb potential experienced by the second electron is then a function of the second electron s position along the v-axis (coimecting the Be nucleus and the first electron) and its distance perpendicular to the v-axis. For simplicity, this second electron... 

Figure B3.1.5. Probability (as a fimction of angle) for finding the seeond eleetron in He when both eleetrons are loeated at the maximum in the Is orbital s probability density. The bottom line is that obtained using a Hylleraas-type fiinetion, and the other related to a highly-eorrelated multieonfigurational wavefLinetion. After [22],...

By expressing the mean-field interaction of an electron at r with the N- 1 other electrons in temis of a probability density pyy r ) that is independent of the fact that another electron resides at r, the mean-field models ignore spatial correlations among the electrons. In reality, as shown in figure B3.T5 the conditional probability density for finding one ofA - 1 electrons at r, given that one electron is at r depends on r. The absence of a spatial correlation is a direct consequence of the spin-orbital product nature of the mean-field wavefiinctions... 

Figure B3.3.5. Energy distributions. The probability density is proportional to the product of the density of states and the Boltzmaim factor.

A way of looking at the points raised in the previous section is to compare energy distributions in two systems whose free energies we wish to relate. In particular, consider measuring, in a simulation of system 0, the fiinction Pq(AE), i.e., the probability density per unit AE of configurations for which and differ by the... 

Bruce A D 1981 Probability density functions for collective coordinates in Ising-like systems J. Phys. O Soiid State Phys. 14 3667-88... 

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