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DARPA Oasis PI Meeting Santa Rosa, CA August 2002 General Progress Report Complex Problems Group University of South Carolina Joseph E. Johnson, PhD DARPA OASIS PI Meeting Santa Rosa CA - Hilton Monday August 19, 2002 Overview System replication for non-network threats Network behavior sought: normal / aberrant Network analysis – wavelets & dimensionality Network classification – Markov type groups Markov type group representations New variables that are measures of the network topology Especially entropy/information measures on graphs As a basis for logical & numerical uncertainty To extend Shannon information measure To seek clusters To define optimal wavelet basis Some Details Our current activity Objectives To utilize new network parameters that characterize the network topology, especially new entropy/information measures that will: Help characterize networks flows: statics & dynamics in real time Define clusters & structures for static graphs Suggest the best basis for wavelet decompositions By helping define the critical network dimensions (variables) Which with multiple time scales defined by complexity theory Provide sensitivity to aberrant network dynamics And thus which will allow a network to be monitored in real time with very rapid detection of and isolation of intrusion. System replication for non-network threats Our group built IRIS, the emergency management information system used by SC Replication of IRIS has been studied & performed USC, UU, Maui IRIS is now being totally rewritten in a Java environment (esp. struts & multi-tier) to achieve isolation of components (ready by Dec 2002) IRIS has modules for: Donated Goods, Critical Facilities, WMD, Voice Recognition, Mapping, Administration, Security, Damage Tracking, and Person Tracking I Network behavior sought: normal / aberrant Network analysis: wavelets & dimensionality Network classification Markov type groups Markov type group representations As a basis for logical & numerical uncertainty To extend Shannon information measure New variables that are measures of the network topology Especially entropy/information measures on graphs To seek clusters To define optimal wavelet basis Some of the Details Lie Groups and Lie Algebras 1. 2. 3. Group theory provides a representation of both exact and approximate symmetries using continuous and discrete transformations. Groups have a multiplication operation with closure, associatively, a unit, and an inverse. Lie Groups / Lie Algebras represent transformations that are continuously connected to the identity. Examples: Rotation Group x2 + y2 + z2 is invariant Lorentz Group c2t2 - x2 - y2 - z2 is invariant (relativity). Poincare Group c2dt2 - dx2 - dy2 - dz2 is invariant thus allowing translations. Unitary Group x*x + y*y + …. Or <a|b> invariant including SU3, SUn (quantum mechanics) Heisenberg Lie Algebra [x,p] = I Creation & annihilation algebra [a+r,as] = Irs Introduction to Markov Processes Markov Transformations A Markov matrix transformation M preserves the sum of the non-negative components of a vector upon which it acts with no negative transformed components (thus x + y + z + w +… is invariant) . It follows that a Markov transformation must itself have nonnegative components with the sum of elements in each column equal to 1. Markov transformations have no inverse and thus they do not form a group. Markov transformations are useful in a variety of problems: such as economic and population redistribution. Markov transformation represent diffusion of the conserved component such as information and thus increases entropy. Markov Type Lie Groups (Johnson J.E., Jour. Math. Phys.1985) In the paper above, I suggested relaxing the non-negative condition to get a ‘Markov like’ Lie Group that preserves Sum xi but which allows for unphysical components. A careful choice of the associated Lie Algebra generators Lij gives Markov transformations when non-negative combinations of Lij are used to generate the transformation. Thus the term: Markov-Type Lie Algebra or Group One can see the connection to diffusion. The lack of an inverse results in a loss of ‘information’. Lij along with Lii diagonal generators form a basis of GL(n,R) = Markov Subgroup M(n,R) + an Abelian Scale (growth) group A(n,r) – a new decomposition of GL(n,R). Network or Graph Theory Adjacency (or Connectivity) Matrix for a Network (graph) An undirected graph consists of a set of points or nodes (numbered 1, 2, …) connected by lines. If node i is connected to node j then we represent this with a matrix Lij = 1 else =0. Thus Lij contains the topological connectivity of the graph. The diagonal Lii is taken as 0 or 1 if a node is considered to be (or not to be) connected to itself. It also contains the superfluous numbering of nodes. It is an unsolved problem to tell, from Lij, if two graphs are topologically equivalent. A Network as a MarkovDynamical Informational Flow If we take the diagonal elements of the connectivity matrix so that the sum over each column is ‘0’ then Lij is a Markov Lie algebra generator for a transformation that preserves a vector sum xi. We could take this vector to be the information stored at the node xi or water or electrical charge or whatever. This gives us a dynamical system where information is moved from node to node by equal bandwidth by all connections. L is the time evolution operator with x(t) = exp(tL). The eigenvectors are linear combinations of nodes with information content decreasing at the rate of exp(tz) where z is the associated eigenvalue. There is a strong analogy with exp(tH) in quantum theory. Network Dynamics This work extends the customary graph theory with the associated model of information (or water or population) flow of a conserved quantity. Thus one now has a dynamical physical model and interpretation for the connectivity matrix as well as the power of Lie group theory that can be applied to network dynamics and topology. The choice of 0 or 1 as diagonal elements can also be achieved within this theory and represents exponential growth or decay of the quantity at that node. This also has the interpretation of forbidding or inducing a revisit to a given node in the transitions. Asymmetric & Directed Graphs & Information Nonconservation We can readily extend this work to dynamical problems on: Different data transfer rates between nodes where Lij is not equal to 1 but is still symmetric. Directed graphs where Lij is not symmetric (but rather has the values 0 and 1 indicating flow direction). Graphs which allow for the creation and annihilation of information at the nodal points. With these collective generalizations, one obtains the transformations of GL(n,R) with a restricted Lie algebra parameter space. An Approach to Network Classification Self Connectivity Defined It is known that these eigenvalue sets are almost but not quite isomorphic to the topologically different graphs as some graphs are isospectral. Define L1ij = 1 or 0 as before when i and j are not equal. Save the diagonal vector and reset the diagonal terms =0 because we do not want to allow a transition from a node back to itself. Now define L2 = L1 L1 via normal matrix multiplication and set the diagonal terms =0. Then define L3 = L1 L2 + L2 L1 , etc up to L2n-2 where n is the number of nodes. This gives a sequence of 2n-2 matrices. We require 2n-2 possible transitions to ‘feel out’ the paths from a node and back to that node again. We now extract the diagonal components to construct an (2n-2) x n matrix with columns labeled by node number and the rows labeled by the power of the matrix. Self-Connectivity Matrix Defined We now reorder the columns by sorting the values (ascending) in order of the first row. Then for each set of identical values in the first row, we resort the columns in the second row (ascending). The final matrix gives a relatively unique order to the nodes but it is not proven that it is unique. To the extent that the new column order is unique, one obtains a natural numbering of the nodes. This matrix will constitute the first part of identification of the topology. We call this the Self-Connectivity Matrix. Interconnectivity Matrices Defined Return now to the first n powers of L including the first power. Note that each power is a symmetrized product of matrices and thus is symmetric and has real eigenvalues. We call this the n^2 matrix of eigenvalues, the interconnectivity eigenvalue matrix as it describes interconnectivities. It is independent of the numbering of the nodes. Each of the eigenvalue sets represents the normal nodes of a Markov transformation that takes n steps as an infinitesimal motion. Set all diagonal values equal to the negative of the sum of the remaining column elements in that matrix thus giving a set of Markov Lie generators. Find the eigenvalues and eigenvectors of these matrices and group these n eigenvectors as rows in a new matrix and sort each row by ascending associated eigenvalues (placed in an associated column ‘0’) for each power. This gives an (n+1) x n^2 matrix of the eigenvalues and eigenvectors that correspond to dynamic evolution of the system when one dynamically evolves with multiple node connectivity. Graph Description Neither the n x (2n-1) self connectivity matrix nor the n x n interconnectivity eigenvalues are dependent upon the ordering of the nodes but only on the topology. It is our hope that this removes much of the isospectral aspects of a graphs description. We would adjoin the sequence of eigenvector matrices at each of the n levels where one sorts the rows by ascending order of the associated eigenvalues, for each power, and sorts the columns by the node ordering prescribed by the final ordering that results from the self connectivity matrix as described above. Any degeneracy that remains from the self-connectivity matrix is to be resolved by ordering the components of the eigenvectors by the lowest order values that differ. We are studying the extent to which this method removes the degeneracy's and identifies the topology of the graph. We are also studying the utility of the connectivity matrix as a Lie generator for transformation flows of information on a network. Current Activity Study the self connectivities and eigenvalues of the interconnectivity matrix as possible dimensions sensitive to network dynamics Study these variables as a way to identify the optimal wavelet basis functions for describing network dynamics Identify variables with the maximum sensitivities to normal verses aberrant behavior. Thank You The Importance of Lie Algebras We note that the foundations of each of the important physical theories are related to a Lie algebra (or group). Is there another Lie algebra that is critical and foundational ? Maybe general relativity, string theory, a theory of everything, Let us consider a set of problems that is somewhat intriguing: Information Information is closely related to entropy – and is often called negentropy I = - ln P. Information is related to order just as entropy is related to disorder thus to study one is to study another. Entropy gives a direction to time by the second law of thermodynamics. But according to physical laws we have time reversal invariance. But we all know that this is no conflict because it is just ‘improbable’ to reverse a system and achieve decreased entropy. Information - problems All scientific measurements contain error and are represented by ‘numbers’, actually pairs of numbers, that represent a mean value and the error. But these distributions do not close under +-*/. The human mind is so incredible because it can manage fuzzy logic, fuzzy calculations, and numerical uncertainty. But there is no clear mathematical structure on how to do this. How does a living organism advance in time, increasing order, while fighting entropy. Do we really know how to define information below 1/0 ? Information – more problems If so why cannot we just program a computer to compute a series expansion or subroutine ‘as long as it contributes to the information of the term being computed? How much information is in the value: An 81% chance of rain. How do we effectively computer the cost or value ($) of information. Do we really have a grasp on how mathematical operations degrade information when acting on uncertain numbers? Are there optimal computational paths? Information – still more problems Consider the measurement problem in quantum mechanics: Do we all feel confident that we exactly and mathematically understand the information gained in a measurement? To me it seems intractably difficult to get to the bottom of the entanglement between a quantum system interacting with a classical measuring system that extracts ‘information’ and forces it into a state. Information from a Lie group? Obviously group theory cannot help because a group always has an inverse. Since one cannot undo entropy and diffusion then a group is not a reasonable avenue. But I will contend that a Lie group might give the same insight into Information and all of these problems as was the case elsewhere in physics. A Lie Algebra of ‘Information’ When we look at diffusion, we perform a transformation that shifts things around but maintains the total sum of things. My talk will center on transformations that leave the sum of non-negative values invariant: x + y + z + …. The Markov “Group”