This thesis focuses on the study of correlations in multispecies totally and
partially asymmetric exclusion processes (TASEPs and PASEPs). We study various
models, such as multispecies TASEP on a continuous ring, multispecies PASEP on
a ring, multispecies B-TASEP, and multispecies TASEP on a ring with multiple
copies of each particle. The primary goal of this thesis is to understand the
two-point correlations of adjacent particles in these processes.
The details of the results are as follows:
We first discuss the multispecies TASEP on a continuous ring and prove a conjecture
by Aas and Linusson (AIHPD, 2018) regarding the two-point correlation of adjacent
particles. We use the theory of multiline queues developed by Ferrari and Martin
(Ann. Probab., 2007) to interpret the conjecture in terms of the placements of numbers
in triangular arrays. Additionally, we use projections to calculate correlations
in the continuous multispecies TASEP using a distribution on these placements.
Next, we prove a formula for the correlation of adjacent particles on the first two
sites in a multispecies PASEP on a finite ring. To prove the results, we use the
multiline process defined by Martin (Electron. J. Probab., 2020), which is a
generalisation of the Ferrari-Martin multiline process described above.
We then talk about the multispecies B-TASEP with open boundaries. Aas, Ayyer, Linusson
and Potka (J. Physics A, 2019) conjectured a formula for the correlation between adjacent particles
on the last two sites in a multispecies B-TASEP. To solve this conjecture, we use a
Markov chain that is a 3-species TASEP defined on the Weyl group of type B.
This allows us to make some progress towards the above conjecture.
Finally, we discuss a more general multispecies TASEP with multiple particles for each
species. We extend the results of Ayyer and Linusson (Trans. AMS., 2017) to this case
and prove formulas for two-point correlations and relate them to the TASEP speed process.