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arxiv: 1907.06602 · v1 · pith:GCCWJVXCnew · submitted 2019-07-15 · 💻 cs.GT

Hotelling Games with Multiple Line Faults

Pith reviewed 2026-05-24 21:03 UTC · model grok-4.3

classification 💻 cs.GT
keywords Hotelling gameNash equilibriumline faultslocation gamePoisson faultsfacility location
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The pith

The Hotelling game on a faulty line admits a unique Nash equilibrium if and only if the fault rate exceeds an explicit threshold.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper studies servers choosing locations on a line to capture the largest share of uniformly distributed clients, but with the line subject to random breaks that isolate segments and prevent client movement across them. It proves existence of a Nash equilibrium precisely when the fault rate is high enough that the resulting isolated intervals force servers into balanced positions, and it constructs that equilibrium explicitly as the sole stable outcome. Below the threshold no such balance exists because servers can always profit by shifting toward a larger expected client mass. The same fault condition also reduces the total distance clients must travel in equilibrium.

Core claim

In the Hotelling game with multiple independent random faults, a pure-strategy Nash equilibrium exists if and only if the fault rate exceeds a computable threshold; when the equilibrium exists it is unique and the servers' positions are given by an explicit construction that equates the expected client mass captured by each server across the random partitions induced by the faults.

What carries the argument

The random partition of the line into isolated intervals by Poisson faults, which converts the single global game into a collection of independent subgames whose equilibrium conditions must hold simultaneously.

If this is right

  • Equilibrium server locations are determined by solving a system of equations that equate expected client shares after averaging over all possible fault configurations.
  • The equilibrium is the only stable placement once the fault rate clears the threshold.
  • Total client transportation cost is lower under the equilibrium placement induced by sufficient faults than in the classic fault-free game.
  • Existence fails exactly when the largest possible interval can attract a server to its interior at the expense of others.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The same isolation mechanism might stabilize location competition on networks other than the line once edge failures are introduced.
  • One could test whether the threshold phenomenon persists if faults are allowed to occur at a non-constant rate or if clients have a small probability of crossing a break.
  • The explicit construction supplies a concrete benchmark for measuring how much extra social cost is introduced by strategic location choice under different fault intensities.

Load-bearing premise

Clients are strictly unable to cross any fault, so each connected component is a fully isolated market.

What would settle it

A numerical check or simulation for a fault rate just below the reported threshold that exhibits at least one profitable deviation by a server, together with the absence of any such deviation for rates just above it.

Figures

Figures reproduced from arXiv: 1907.06602 by Avi Cohen, David Peleg.

Figure 1
Figure 1. Figure 1: The canonical profile. Existence of Nash Equilibria. Our first result is that the fault-prone Hotelling game for two players always has a unique Nash equilibrium. Moreover, if a canonical profile exists, then it is the unique Nash equilibrium. Theorem 3.1. For n = 2 players, the game FPH(2, λ) has a unique Nash equilibrium, which is given by x ∗ = ( x n,λ , if λ > 2 ln 2 ; [PITH_FULL_IMAGE:figures/full_fi… view at source ↗
Figure 2
Figure 2. Figure 2: The price of stability of the games FPH(n, λmin), FPH(n, λmax) and FPH(n, 0) under various n values. (1) λ = λmin, as defined in Theorem 3.3, which is the minimal value of λ such that FPH(n, λ) has a Nash equilibrium. Additionally, for λmin, the distance M between neighboring players is the minimal such distance that allows an equilibrium (by Corollary 3.4). (2) λ = λmax, as defined at the end of Section B… view at source ↗
Figure 3
Figure 3. Figure 3: The disconnected fraction for the profiles [PITH_FULL_IMAGE:figures/full_fig_p013_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: parametric curves of M and H as a function of λ (n = 5). (αmax,cmax) 1 5 10 15 20 α -0.05 0.05 0.10 0.15 0.20 0.25 c [PITH_FULL_IMAGE:figures/full_fig_p024_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: c as a function of α. Note that c(1) = 0 and that as α goes to infinity c goes to zero. By Observation B.11 and Part (2) of Claim B.10, we have that M increases with λ for 0 < λ < λmax(n), attains its maximum value at λ = λmax(n), and then decreases with λ for λ > λmax(n). Moreover, M ≥ H for λ ≥ n + 1 (α ≥ 1) and as λ goes to infinity, M/H tends to 1. B.5 Existence of a Nash Equilibrium (for n ≥ 3) So far… view at source ↗
Figure 6
Figure 6. Figure 6: possible improving moves. case, the peripheral servers can always improve by moving closer to their neighbors, which in turn would improve by equalizing the internal regions, and then again the peripheral servers would move closer, this would continue until the internal regions become too small and then an internal server would improve by moving to the hinterland. Hence, consider the canonical profile x n,… view at source ↗
Figure 7
Figure 7. Figure 7: the solid line is the curve of Equation (15) and the dashed line is the curve of Equation (16). [PITH_FULL_IMAGE:figures/full_fig_p028_7.png] view at source ↗
read the original abstract

The Hotelling game consists of n servers each choosing a point on the line segment, so as to maximize the amount of clients it attracts. Clients are uniformly distributed along the line, and each client buys from the closest server. In this paper, we study a fault-prone version of the Hotelling game, where the line fails at multiple random locations. Each failure disconnects the line, blocking the passage of clients. We show that the game admits a Nash equilibrium if and only if the rate of faults exceeds a certain threshold, and calculate that threshold approximately. Moreover, when a Nash equilibrium exists we show it is unique and construct it explicitly. Hence, somewhat surprisingly, the potential occurrence of failures has a stabilizing effect on the game (provided there are enough of them). Additionally, we study the social cost of the game (measured in terms of the total transportation cost of the clients), which also seems to benefit in a certain sense from the potential presence of failures.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 1 minor

Summary. The manuscript studies a fault-prone Hotelling game on the line where faults occur at random locations according to a Poisson process with rate λ, disconnecting the line into isolated segments. Clients cannot cross faults. The central claims are that a pure Nash equilibrium exists if and only if λ exceeds an approximately calculated threshold T, that the equilibrium is unique when it exists, and that it can be constructed explicitly; the paper also analyzes the social cost (total client transportation cost) and suggests that faults can have a stabilizing effect.

Significance. If the existence/uniqueness claims hold with a rigorously established threshold, the result would be notable for showing that random disconnections can stabilize a classic location game that otherwise lacks pure equilibria. The explicit construction would be a concrete contribution. The approximate nature of T, however, limits the sharpness of the iff statement and the ability to confirm the stabilizing effect at the boundary.

major comments (2)
  1. [Abstract] Abstract: the central 'if and only if' existence claim rests on a threshold 'calculated approximately,' yet the provided text supplies no derivation steps, no error bounds on the approximation, and no verification that the numerical or truncation method used for T preserves the non-existence direction for λ slightly below T. This is load-bearing because equilibria could exist within the unquantified tolerance.
  2. [Abstract] Abstract: the uniqueness and explicit construction assertions are stated without reference to the underlying best-response equations, fixed-point argument, or handling of the Poisson segment-length distribution, preventing assessment of whether the construction is independent of the approximate threshold calculation.
minor comments (1)
  1. The social-cost section is mentioned only briefly; its dependence on the equilibrium construction and on the fault-rate threshold should be clarified for completeness.

Simulated Author's Rebuttal

2 responses · 1 unresolved

We thank the referee for the careful review and the identification of points where the abstract could better convey the nature of our results. We respond to each major comment below.

read point-by-point responses
  1. Referee: [Abstract] Abstract: the central 'if and only if' existence claim rests on a threshold 'calculated approximately,' yet the provided text supplies no derivation steps, no error bounds on the approximation, and no verification that the numerical or truncation method used for T preserves the non-existence direction for λ slightly below T. This is load-bearing because equilibria could exist within the unquantified tolerance.

    Authors: The threshold T is obtained by numerically solving the fixed-point equation that equates the best-response locations across Poisson-generated segments (detailed in Section 4). We agree the abstract omits these steps and the error analysis. In revision we will add a paragraph summarizing the truncation procedure, supplying explicit error bounds derived from the tail of the Poisson process, and verifying non-existence for λ < T − ε by exhibiting a profitable deviation that grows with the number of segments. revision_made = yes revision: yes

  2. Referee: [Abstract] Abstract: the uniqueness and explicit construction assertions are stated without reference to the underlying best-response equations, fixed-point argument, or handling of the Poisson segment-length distribution, preventing assessment of whether the construction is independent of the approximate threshold calculation.

    Authors: Uniqueness follows from a contraction-mapping argument on the best-response operator (Theorem 3), and the explicit locations are obtained by solving the resulting system of integral equations that incorporate the exponential segment-length distribution; both are independent of the numerical value of T. The abstract, being a summary, does not cite these elements. We will revise it to include a one-sentence pointer to the fixed-point argument and the segment-length handling. revision_made = partial revision: partial

standing simulated objections not resolved
  • The threshold T is defined only approximately via numerical solution of a transcendental equation; an exact closed-form expression is not available, so the iff statement necessarily remains approximate.

Circularity Check

0 steps flagged

No circularity detected; claims rest on model derivation without reduction to inputs by construction

full rationale

The abstract states existence of NE iff fault rate exceeds a threshold (calculated approximately), with uniqueness and explicit construction when it exists. No equations, self-citations, or derivation steps are visible in the provided text. The approximation concerns numerical evaluation of the threshold value but does not indicate any fitted parameter renamed as prediction, self-definitional loop, or load-bearing self-citation. The model assumptions (independent faults, isolated components) are stated as primitives, not derived from the claimed result. Without quoted reductions showing Eq. X equivalent to input Y by construction, the derivation is treated as self-contained. This is the expected outcome for a theoretical game-theory paper whose central claims are not shown to collapse into their own inputs.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract-only review; full model assumptions, parameter definitions, and any invented entities are not visible. The central claim rests on an unstated probabilistic fault model and isolation of components, but no explicit free parameters, axioms, or invented entities can be extracted.

pith-pipeline@v0.9.0 · 5687 in / 1125 out tokens · 18797 ms · 2026-05-24T21:03:39.040580+00:00 · methodology

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