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In mathematics — specifically, in large deviations theory — the **tilted large deviation principle** is a result that allows one to generate a new large deviation principle from an old one by exponential tilting, i.e. integration against an exponential functional. It can be seen as an alternative formulation of Varadhan's lemma.

Let *X* be a Polish space (i.e., a separable, completely metrizable topological space), and let (*μ*_{ε})_{ε>0} be a family of probability measures on *X* that satisfies the large deviation principle with rate function *I* : *X* → [0, +∞]. Let *F* : *X* → **R** be a continuous function that is bounded from above. For each Borel set *S* ⊆ *X*, let

and define a new family of probability measures (*ν*_{ε})_{ε>0} on *X* by

Then (*ν*_{ε})_{ε>0} satisfies the large deviation principle on *X* with rate function *I*^{F} : *X* → [0, +∞] given by

In mathematical analysis, the **Dirac delta function**, also known as the **unit impulse**, is a generalized function on the real numbers, whose value is zero everywhere except at zero, and whose integral over the entire real line is equal to one. Since there is no function having this property, to model the delta "function" rigorously involves the use of limits or, as is common in mathematics, measure theory and the theory of distributions.

**Vapnik–Chervonenkis theory** was developed during 1960–1990 by Vladimir Vapnik and Alexey Chervonenkis. The theory is a form of computational learning theory, which attempts to explain the learning process from a statistical point of view.

**Mathematical morphology** (**MM**) is a theory and technique for the analysis and processing of geometrical structures, based on set theory, lattice theory, topology, and random functions. MM is most commonly applied to digital images, but it can be employed as well on graphs, surface meshes, solids, and many other spatial structures.

In mathematics, the **Radon–Nikodym theorem** is a result in measure theory that expresses the relationship between two measures defined on the same measurable space. A *measure* is a set function that assigns a consistent magnitude to the measurable subsets of a measurable space. Examples of a measure include area and volume, where the subsets are sets of points; or the probability of an event, which is a subset of possible outcomes within a wider probability space.

The **path integral formulation** is a description in quantum mechanics that generalizes the stationary action principle of classical mechanics. It replaces the classical notion of a single, unique classical trajectory for a system with a sum, or functional integral, over an infinity of quantum-mechanically possible trajectories to compute a quantum amplitude.

In probability theory, a **Chernoff bound** is an exponentially decreasing upper bound on the tail of a random variable based on its moment generating function. The minimum of all such exponential bounds forms *the* Chernoff or **Chernoff-Cramér bound**, which may decay faster than exponential. It is especially useful for sums of independent random variables, such as sums of Bernoulli random variables.

In the mathematical field of real analysis, **Lusin's theorem** or **Lusin's criterion** states that an almost-everywhere finite function is measurable if and only if it is a continuous function on nearly all its domain. In the informal formulation of J. E. Littlewood, "every measurable function is nearly continuous".

In mathematics — specifically, in large deviations theory — a **rate function** is a function used to quantify the probabilities of rare events. Such functions are used to formulate **large deviation principles**. A large deviation principle quantifies the asymptotic probability of rare events for a sequence of probabilities.

In the theory of probability, the **Glivenko–Cantelli theorem**, named after Valery Ivanovich Glivenko and Francesco Paolo Cantelli, describes the asymptotic behaviour of the empirical distribution function as the number of independent and identically distributed observations grows. Specifically, the empirical distribution function converges uniformly to the true distribution function almost surely.

In the mathematical theory of probability, a **Doob martingale** is a stochastic process that approximates a given random variable and has the martingale property with respect to the given filtration. It may be thought of as the evolving sequence of best approximations to the random variable based on information accumulated up to a certain time.

In mathematics, **tightness** is a concept in measure theory. The intuitive idea is that a given collection of measures does not "escape to infinity".

In probability theory and theoretical computer science, **McDiarmid's inequality** is a concentration inequality which bounds the deviation between the sampled value and the expected value of certain functions when they are evaluated on independent random variables. McDiarmid's inequality applies to functions that satisfy a *bounded differences* property, meaning that replacing a single argument to the function while leaving all other arguments unchanged cannot cause too large of a change in the value of the function.

In mathematics, **uniform integrability** is an important concept in real analysis, functional analysis and measure theory, and plays a vital role in the theory of martingales.

In mathematics, **Laplace's principle** is a basic theorem in large deviations theory which is similar to Varadhan's lemma. It gives an asymptotic expression for the Lebesgue integral of exp(−*θφ*(*x*)) over a fixed set *A* as *θ* becomes large. Such expressions can be used, for example, in statistical mechanics to determining the limiting behaviour of a system as the temperature tends to absolute zero.

In mathematics, **Schilder's theorem** is a generalization of the Laplace method from integrals on to functional Wiener integration. The theorem is used in the large deviations theory of stochastic processes. Roughly speaking, out of Schilder's theorem one gets an estimate for the probability that a (scaled-down) sample path of Brownian motion will stray far from the mean path. This statement is made precise using rate functions. Schilder's theorem is generalized by the Freidlin–Wentzell theorem for Itō diffusions.

In mathematics, the **Freidlin–Wentzell theorem** is a result in the large deviations theory of stochastic processes. Roughly speaking, the Freidlin–Wentzell theorem gives an estimate for the probability that a (scaled-down) sample path of an Itō diffusion will stray far from the mean path. This statement is made precise using rate functions. The Freidlin–Wentzell theorem generalizes Schilder's theorem for standard Brownian motion.

In mathematics, the **Dawson–Gärtner theorem** is a result in large deviations theory. Heuristically speaking, the Dawson–Gärtner theorem allows one to transport a large deviation principle on a “smaller” topological space to a “larger” one.

In mathematics, **Varadhan's lemma** is a result from the large deviations theory named after S. R. Srinivasa Varadhan. The result gives information on the asymptotic distribution of a statistic *φ*(*Z*_{ε}) of a family of random variables *Z*_{ε} as *ε* becomes small in terms of a rate function for the variables.

In mathematics — specifically, in large deviations theory — the **contraction principle** is a theorem that states how a large deviation principle on one space "pushes forward" to a large deviation principle on another space *via* a continuous function.

In mathematics, **exponential equivalence of measures** is how two sequences or families of probability measures are "the same" from the point of view of large deviations theory.

- den Hollander, Frank (2000).
*Large deviations*. Fields Institute Monographs 14. Providence, RI: American Mathematical Society. pp. x+143. ISBN 0-8218-1989-5. MR 1739680

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