
Inverse thermodynamic uncertainty relations: general upper bounds on the
fluctuations of trajectory observables
George Bakewell-Smith,1Federico Girotti,1M˘ad˘alin Gut¸˘a,1, 2 and Juan P. Garrahan3, 2
1School of Mathematical Sciences, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
2Centre for the Mathematics and Theoretical Physics of Quantum Non-Equilibrium Systems,
University of Nottingham, Nottingham, NG7 2RD, UK
3School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD, UK
Thermodynamic uncertainty relations (TURs) are general lower bounds on the size of fluctutations
of dynamical observables. They have important consequences, one being that the precision of
estimation of a current is limited by the amount of entropy production. Here we prove the existence
of general upper bounds on the size of fluctuations of any linear combination of fluxes (including
all time-integrated currents or dynamical activities) for continuous-time Markov chains. We obtain
these general relations by means of concentration bound techniques. These “inverse TURs” are
valid for all times and not only in the long time limit. We illustrate our analytical results with a
simple model, and discuss wider implications of these new relations.
Introduction. Thermodynamic uncertainty relations
(TURs) refer to a class of general lower bounds on the
size of fluctuations in the observables of trajectories of
stochastic systems. TURs were initially postulated as a
bound on the scaled variance of time-averaged currents
in the stationary state of continuous-time Markov chains
[1], and soon after proven (using “level 2.5” large devi-
ation methods [2–4]) to apply to the whole probability
distribution [5]. TURs were subsequently generalised to
various other dynamics and observables, including for fi-
nite times [6, 7], for discrete-time Markov dynamics [8],
for the fluctuations of first-passage times [9, 10] and for
open quantum systems [11–14], among many other ex-
tensions and alternative derivations (see for example [15–
24]). For a review see [25].
The most widely considered form of the TUR is for
the relative uncertainty (variance over mean squared) of
a time-integrated current being larger than (twice) the
inverse of the entropy production. This has immediate
dual consequences for inference and estimation [1, 25]:
increased precision in the estimation of the value of a
current from a stochastic trajectory requires increasing
the dissipation, or alternatively, the value of the entropy
production can be inferred from the fluctuations of one
or more specific currents which might be easier to ac-
cess. Similar uses of the TUR can be formulated using
the dynamical activity [26–28] for the estimation of time-
symmetric observables [9, 25].
Despite their success and generality, a limitation of
TURs is that they only provide lower bounds on the size
of fluctuations: except in the few cases where they are
tight, inference on the observable of interest is hindered
by the absence of a corresponding upper bound. Here
we correct this issue by introducing a class of general up-
per bounds for fluctuations of trajectory observables con-
sisting of linear combination of fluxes (number of jumps
between configurations [2]) of a continuous-time Markov
chain, which includes all currents and activities. For lack
of a better name, we call these “inverse thermodynamic
uncertainty relations”. The inverse TURs are valid for
all times, and like the large deviation formulation of the
TURs, they bound fluctuations at all levels. We prove
these general relations using concentration bound tech-
niques [29–34].
Notation and definitions. Let X:= (Xt)t≥0be a
continuous-time Markov chain taking values in the finite
state space Ewith generator W=Px6=ywxy|xihy| −
Pxwxx|xihx|, with x, y ∈E. If X0is distributed accord-
ing to some probability measure νon the state space,
we denote by Pνthe law of Xand we use Eνfor the
corresponding expected value. We assume that Xis ir-
reducible with unique invariant measure (i.e. stationary
state) π. We are interested in studying fluctuations of
observables of the trajectory Xof the form
A(t) = X
x6=y
axyNxy(t),
where axy are arbitrary real numbers with P|axy|>0,
and Nxy(t) are the elementary fluxes, that is, the num-
ber of jumps from xto yup to time tin X. For a
time-integrated current the coefficients are antisymmet-
ric, while for counting observables (such as the activity),
they are symmetric.
The fluctuations of A(t) in the long time satisfy the
following theorems [35]:
(i) Strong Law of Large Numbers (holds almost surely)
lim
t→+∞
A(t)
t=haiπ:= X
x6=y
πxwxyaxy.
(iii) Central Limit Theorem (small deviations; holds in
distribution)
lim
t→+∞
A(t)−thaiπ
√t=N(0, σ2
∞)
where σ2
∞= limt→+∞σ2
ν(t)/t and σ2
ν(t) is the variance of
A(t) if νis the initial distribution (notice, however, that
arXiv:2210.04983v1 [cond-mat.stat-mech] 10 Oct 2022