I am trying to understand what, probabilistically, a random permutation of a finite list of random variables is, and I tried to draw some ideas from stopped random sequences. For example, seeing a list of random variables $X=\{X_1,\ldots,X_N\}$ as measurable map from $\Omega\times[N]\longrightarrow\mathbb{R}$ (the typical approach in stochastic processes: seeing $X_n(\omega)$ as $X(\omega,n)$) works when defining the stopped sequence $X^\tau$ at random time $\tau\in[N]$, by composing the measurable map with the map which sends $\omega$ into $(\omega,\tau(\omega))$. It is easy to show that this composition, is still a measurable random variable $X_\tau=X_{\tau(\omega)}(\omega)$. I would like to do something similar by considering a randomly permuted list (say by a random permutation $\pi\in S_N$, which we can see in one-line notation as $(\pi_1,\ldots,\pi_N)$), but here I find a difficulty: I cannot start with the same map $\Omega\times[N]\longrightarrow\mathbb{R}$ as a point of view for my list, because I need a notion of order, to get to $X^\pi=\{X_{\pi_1},\ldots,X_{\pi_N}\}$. So I considered seeing an ordered list of random variables as a map from $\Omega\times S_N$ to $\mathbb{R}^N$, that is it sends $(\omega, \pi)$ into $(X_{\pi_1}(\omega),\ldots,X_{\pi_N}(\omega))$. The original list is obtained with $\pi=id$. Then I can see the randomly permuted list $X^\pi$ as a composition of this map with the map that sends $\omega$ into $(\omega,\pi(\omega))$, yielding the desired $(X_{\pi_1(\omega)}(\omega),\ldots,X_{\pi_N(\omega)}(\omega))$. My first question is: is there a more economic approach to this? EDIT: I came to think there might actually be. By also seeing a random permutation as a vector, through its one-line notation, that is a map from $\Omega\times [N+1]$ to $[N+1]$, sending $(\omega,n)$ into $\pi_n(\omega)$, we can exploit the usual map that adds $\omega$ in the first component instead of simply using the permutation, and compose it with the standard point of view of stochastic processes earlier described: thus we define $X^\pi$ as the composition of the map sending $(\omega,n)$ into $(\omega,\pi_n(\omega))$ first and the one sending $(\omega,m)$ into $X_m(\omega)$ secondly, thus achieving $X_{\pi_n(\omega)}(\omega)$. The overall composition goes from $\Omega\times [N+1]$ to $\mathbb{R}$ and is therefore a random vector (it passes through $\Omega\times [N+1]$ in the middle step so it is a valid composition). It seems that these maps that doubles the $\omega$ argument (like $(\omega,\pi_n(\omega))$) are quite useful in these kinds of constructions. Do they have a name and a standard notation?
2026-04-04 01:19:42.1775265582
A construction of permuted stochastic sequences
42 Views Asked by Bumbble Comm https://math.techqa.club/user/bumbble-comm/detail AtRelated Questions in PROBABILITY
- How to prove $\lim_{n \rightarrow\infty} e^{-n}\sum_{k=0}^{n}\frac{n^k}{k!} = \frac{1}{2}$?
- Is this a commonly known paradox?
- What's $P(A_1\cap A_2\cap A_3\cap A_4) $?
- Prove or disprove the following inequality
- Another application of the Central Limit Theorem
- Given is $2$ dimensional random variable $(X,Y)$ with table. Determine the correlation between $X$ and $Y$
- A random point $(a,b)$ is uniformly distributed in a unit square $K=[(u,v):0<u<1,0<v<1]$
- proving Kochen-Stone lemma...
- Solution Check. (Probability)
- Interpreting stationary distribution $P_{\infty}(X,V)$ of a random process
Related Questions in STOCHASTIC-PROCESSES
- Interpreting stationary distribution $P_{\infty}(X,V)$ of a random process
- Probability being in the same state
- Random variables coincide
- Reference request for a lemma on the expected value of Hermitian polynomials of Gaussian random variables.
- Why does there exists a random variable $x^n(t,\omega')$ such that $x_{k_r}^n$ converges to it
- Compute the covariance of $W_t$ and $B_t=\int_0^t\mathrm{sgn}(W)dW$, for a Brownian motion $W$
- Why has $\sup_{s \in (0,t)} B_s$ the same distribution as $\sup_{s \in (0,t)} B_s-B_t$ for a Brownian motion $(B_t)_{t \geq 0}$?
- What is the name of the operation where a sequence of RV's form the parameters for the subsequent one?
- Markov property vs. transition function
- Variance of the integral of a stochastic process multiplied by a weighting function
Related Questions in PERMUTATIONS
- A weird automorphism
- List Conjugacy Classes in GAP?
- Permutation does not change if we multiply by left by another group element?
- Validating a solution to a combinatorics problem
- Selection of at least one vowel and one consonant
- How to get the missing brick of the proof $A \circ P_\sigma = P_\sigma \circ A$ using permutations?
- Probability of a candidate being selected for a job.
- $S_3$ action on the splitting field of $\mathbb{Q}[x]/(x^3 - x - 1)$
- Expected "overlap" between permutations of a multiset
- Selecting balls from infinite sample with certain conditions
Related Questions in RANDOM-VARIABLES
- Prove that central limit theorem Is applicable to a new sequence
- Random variables in integrals, how to analyze?
- Convergence in distribution of a discretized random variable and generated sigma-algebras
- Determine the repartition of $Y$
- What is the name of concepts that are used to compare two values?
- Convergence of sequences of RV
- $\lim_{n \rightarrow \infty} P(S_n \leq \frac{3n}{2}+\sqrt3n)$
- PDF of the sum of two random variables integrates to >1
- Another definition for the support of a random variable
- Uniform distribution on the [0,2]
Related Questions in STOPPING-TIMES
- Need to find Conditions to get a (sub-)martingale
- What techniques for proving that a stopping time is finite almost surely?
- Discrete martingale stopping time
- Optional Stopping Theorem for martingales
- Prove that stopped discrete time nonnegative supermartingales are uniformly integrable
- optimal strategy for drawing a deck of cards
- $\frac1n \sum_{i=1}^n W_i(T_i)\to 0$ a.s. for $n\to\infty$
- Brownian Motion Hitting Time of a line with a negative axis intercept
- Random walk with barriers: estimate time since the appearance of a barrier
- Generalizing a proof for the density of stopped subordinators
Trending Questions
- Induction on the number of equations
- How to convince a math teacher of this simple and obvious fact?
- Find $E[XY|Y+Z=1 ]$
- Refuting the Anti-Cantor Cranks
- What are imaginary numbers?
- Determine the adjoint of $\tilde Q(x)$ for $\tilde Q(x)u:=(Qu)(x)$ where $Q:U→L^2(Ω,ℝ^d$ is a Hilbert-Schmidt operator and $U$ is a Hilbert space
- Why does this innovative method of subtraction from a third grader always work?
- How do we know that the number $1$ is not equal to the number $-1$?
- What are the Implications of having VΩ as a model for a theory?
- Defining a Galois Field based on primitive element versus polynomial?
- Can't find the relationship between two columns of numbers. Please Help
- Is computer science a branch of mathematics?
- Is there a bijection of $\mathbb{R}^n$ with itself such that the forward map is connected but the inverse is not?
- Identification of a quadrilateral as a trapezoid, rectangle, or square
- Generator of inertia group in function field extension
Popular # Hahtags
second-order-logic
numerical-methods
puzzle
logic
probability
number-theory
winding-number
real-analysis
integration
calculus
complex-analysis
sequences-and-series
proof-writing
set-theory
functions
homotopy-theory
elementary-number-theory
ordinary-differential-equations
circles
derivatives
game-theory
definite-integrals
elementary-set-theory
limits
multivariable-calculus
geometry
algebraic-number-theory
proof-verification
partial-derivative
algebra-precalculus
Popular Questions
- What is the integral of 1/x?
- How many squares actually ARE in this picture? Is this a trick question with no right answer?
- Is a matrix multiplied with its transpose something special?
- What is the difference between independent and mutually exclusive events?
- Visually stunning math concepts which are easy to explain
- taylor series of $\ln(1+x)$?
- How to tell if a set of vectors spans a space?
- Calculus question taking derivative to find horizontal tangent line
- How to determine if a function is one-to-one?
- Determine if vectors are linearly independent
- What does it mean to have a determinant equal to zero?
- Is this Batman equation for real?
- How to find perpendicular vector to another vector?
- How to find mean and median from histogram
- How many sides does a circle have?