Questions tagged [nash-equilibrium]

A basic solution concept in game theory that requires each player to select their best response to the strategies chosen by others.

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Nash Equilibrium with Constraints on Decision Variables

I am trying to solve a two player game with constraints on decision variables. The general structure looks something like this: $$\max_{x_1} f(x_1, x_2)$$ $$\max_{x_2} g(x_1, x_2)$$ subject to $$x_1 + ...
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(Game Theory) Why is voting for your worst alternative a weakly dominated action?

I don't fully understand why voting for your worst alternative is a weakly dominated action. The question comes from a question I'm working on: "Assume there are three candidates, A,B and C,...
2 votes
1 answer
59 views

Subgame perfect Nash equilibrium when there is a tie in payoffs seems problematic

My question follows from this question: https://math.stackexchange.com/questions/2132846/game-theory-subgame-perfect-nash-equilibrium-in-a-sequential-game-with-identica from Maths stackexchange. Based ...
6 votes
1 answer
750 views

How does the core relate to strong equilibrium?

An allocation is in the core if there's no coalition that blocks it. A strong equilibrium (Aumann, 1959) is a Nash equilibrium in which no coalition, taking the actions of its complements as given, ...
2 votes
1 answer
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Convex Preference in Nash Equilibrium

Arrow Debreu (AD) uses the convex preference (A4 among their four assumptions, also see the assumption IIIc in AD 1954 ECTA) to make general equilibrium (GE) exist, unique, and well-behave. What ...
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What does it mean when an economist talks about "equilibrium"

In economics, there are many equilibrium concepts, like equilibrium under perfect competition, Monopolist equilibrium, competitive equilibrium, general equilibrium, nash equilibrium, equilibrium price,...
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Best response to convex combination of strategies

Suppose that several pure strategies in a 2-individual game have pure strategy best responses. Can we say that best responses to convex combination of those pure strategies still lie in the convex ...
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Two-dimensional hotelling equilibria

Customers are heterogeneous with regard to their preference for quality $q$. Specifically, a customer's utility from buying a product of quality $q$ at price $p$ is $V-p + \lambda q$, with $\lambda$ ...
1 vote
1 answer
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Is a Monopoly equilibrium also a Nash equilibrium?

Consider a monopoly with price power in the market and the demand is a function of price. Can the result of such a monopoly problem be called a nash equilibrium?
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2 answers
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Nash equilibrium in strictly mixed strategies

I have the following statement which I have been said it is false, but I don't understand why: "All finite games have at least one Nash equilibrium in strictly mixed strategies, as long as there ...
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Mixed Strategies in Bayes Nash Equilibrium (Bayesian Battle of the Sexes). Shouldn't it depend on $p$?

I have a question about calculating mixed strategies in a Bayes Nash Equilibrium in a simple 2-player bimatrix game. To demonstrate the issue, consider ``Bayesian Battle of the Sexes.'' Suppose P1 ...
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bargaining game information/equlibria/gametree/normalform

I have a game with two players, player one offers player two one of two cars, car 1(M) has value 2 and car 2 (H) has value 1. Player two can accept (A) or reject (R) the offer. Now I have to answer ...
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Bayes Nash equilibrium distribution

I would like to define a decision rule that is induced by a BNE distribution in a game with a continuum of agents. For that, I have a decision rule $\varphi:\Theta \rightarrow\Delta(\Delta(A))$ that ...
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1 answer
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Game Theory Model needed to model the question whether "not taking the covid vaccine is free-riding"

I am a student and completely new to Game Theory, in fact, it is an additional course for me, I am actually from an entirely different field. I am asked to choose a Game Theory approach to model the ...
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Strategic game with complete informaation

Consider the following strategic game with complete information played by three players. Each player $i ∈ {1, 2, 3}$ chooses her action from $A = \{1, 2, . . . , 10\}$. Utility functions, mapping each ...
4 votes
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Perfect Bayesian Equilibium - Application to game with inconsistent beliefs / no common prior

Does the concept of a Perfect Bayesian Equilibrium apply only to incomplete games with a common prior / consistent belief? In both Bonanno's "Game Theory" and Osborne's "A Course in ...
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Why Sequenial Equilibrium (SE) imposes no restrictions on the off-equilibrium beliefs in the Spence's model?

I read some lectures on the Spence's model. Some (see e.g. P31 of lecture PPT from MIT game thoery course) mention that SE imposes no restrictions on the off-equilibrium beliefs but without proof. I ...
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Are these two definitions of Bayesian Nash Equilibrium equivalent?

Consider a standard game $\Gamma$ with incomplete information. There are $n$ players indexed by $i=1,...,n$. $S_i\equiv \{s_{i1},...,s_{iJ}\}$ is the set of actions of player $i$. $S\equiv \times_{i=1}...
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Extension of Harsanyi Transform for Two-sided Incomplete Information Games to Beliefs with Zero Probability

In the textbook I'm reading "Game Theory - Giacomo Bonanno", one requirement to applying the Harsanyi transform to convert a two-sided incomplete information game to an imperfect information ...
1 vote
1 answer
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Why does the belief over information sets with probability zero matter in Perfect Bayesian Equilibrium?

I'm struggling to understand why the notion of "belief revision" is an important concept. In particular, why does the belief over information sets with probability zero matter? When ...
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1 answer
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Mixed Strategy Nash Equilibrium for this particular 3x3 matrix

Suppose I am given the following matrix: I would like to find all MSNE I started by doing the double underline method to find any PSNE. I discovered that none exist. I then looked at which strategies ...
4 votes
1 answer
58 views

Equivalence from correlated/communication equilibrium to Nash Equilibrium?

Taking into account the seminal papers of Forges and Imre Bárány, they proove a very strong result that gives an exact connection among the communication and the correlation equilibrium solution ...
2 votes
1 answer
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Sequential and Perfect Bayesian Equilibrium: an example?

My question is quite simple. Could someone given an example of how to determine a Sequential Equilibrium given a set of Perfect Bayesian Equilibria? The definition of sequential equilibrium where ...
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Does Subgame Perfect Nash Equilibria (SPNE) allow for credible threats?

Consider the following extensive-form game: In one alternative, Player 2 chooses G and E and Player 1 chooses D. However, Player 2 can increase her gain by making a credible threat and switch from G ...
4 votes
1 answer
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Correlation device that induces a specific transition probability

Taking a look at this paper of Forges and Vida the authors define a correlation device in page $102$, that is a standard probability space $\left(\Omega,\mathcal{B},\mu\right)$, They assume that the ...
1 vote
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What if Bergemann and Morris setting used mixed (or bbehavioral) actions instead of pure actions as reccomendations?

Once again, I will refer to the setting of Bergemann and Morris (2016) and write here the payoff formula of player $i$ from the perspective of the information designer. The payoff formula is the ...
3 votes
1 answer
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Bergemann and Morris information designer and decision rule concept

Taking a look in the paper of Bergemman and Morris in 2016, they refer to the desicion rule as mapping $$\sigma:\Theta\times T\to\Delta(A)$$ The explanation to understand the notion of it is given as ...
5 votes
1 answer
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Prove that for every Nash equilibrium $\sigma^*$, the probability distribution $p_{\sigma^*}$ is a correlated equilibrium

This is a classic theorem in game theory, that is left as an excersice in my textbook. Can anybody proove it? I can not thing of anything excpet from the definition of the correlated equilibrium in ...
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1 answer
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Price competition; finding the equilibrium expression for price and profit

This question deals regarding the price competition between two firms developing products that directly compete on the market. Fundamentally basing on the game theory and the Nash equilibrium, the aim ...
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1 answer
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Bertrand competition with homogenous good and Hotelling's spatial model

Q. There are a 1000 costumers uniformly distributed on [0,3]. Each wants to buy 1 ice-cream. There are two firms which produce ice-cream costlessly and firm i charges p_i. Consumer's effective price ...
3 votes
1 answer
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Bayes correlated equilibrium of Bergemann and Morris

The paper of Bergemann and Morris proves a theorem based on some foundations about the information sets and their expansions. I am trying to understand theorem one intuition, more precisely I cite the ...
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1 answer
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Correlated equilibrium definition

Where can I find the definition of correlated equilibrium apart from here and the seminal paper of Aumman ?
3 votes
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Providing an example in cooperative - games and coalitions

Here is the paper from chich I previously posted another definition here Definition of a $k-$strong Nash Equilibrium I am trying to construct an example to understand the idea of the following ...
5 votes
1 answer
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Nash equilibrium for Bertrand Model with Spatial Differentiation

Consider a town with consumers represented by a closed interval $[0,2]$ with the consumers spread continuously and uniformly. There are two stores, $A$ and $B$ who sell the same product at $p_A$ and $...
2 votes
1 answer
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Definition of a $k-$strong Nash Equilibrium

Consider a game $G=(N, (A^i)_{i\in N}, (g^i)_{i\in N})$, $N=\{1,2,\dots,n\}$, $A=\Pi_{i\in N}A_i$ is the set of actions and $g^i:A\to \mathbb{R}$ is the payoff function. The latter can be extended ...
2 votes
1 answer
166 views

Defining the set of strategies, mixed strategies and the simplex set

Suppose that we have a two players game, where $(S^i)_{i=1}^2$ denotes the set of pure strategies for each one. The set of mixed strategies of player $i$ is denoted by $\Sigma^i=\Delta(S^i)$ while $\...
4 votes
2 answers
380 views

Correlated equilibrium intution

What is the difference between the correlated equilibrium with the mixed strategy Nash equilibrium? Even further, how is this related to the Bayesian correlated equilibrium with complete or incomplete ...
6 votes
1 answer
138 views

Effect of bounding action space on the set of equilibria

Suppose $N$ players play a game, where each player's action space is $[0,1]$. Each player has an identical continuous utility function $u:[0,1]\times [0,1]^{N-1}\rightarrow\mathbb{R}$, where the first ...
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1 answer
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How to find pure strategy NE if you have a n X n matrix (n players) [closed]

Consider the down below which I have trouble with solving. I am not used to find NE for n players, but rather for a simple $2 x 2$ matrix or $3 x 3$, but how does one find NE when you have N players? ...
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1 answer
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Is it possible to find a nash equilibrium that is not an equilibrium in weakly dominant strategy?

I know that it is possible to have a Nash equilibrium which is not an equilibrium in dominant strategy, but is it also applicable for equilibrium in weakly dominant strategy (i.e. a Nash equilibrium ...
6 votes
1 answer
367 views

Relaxing the notion of Nash Equilibrium

Consider a game with $N$ players, each indexed by $i=1,...,N$. Every player $i$ has to choose a $J\times 1$ vector of actions $a_i\equiv (a_{i,1},...,a_{i,J})$ where each $a_{i,j}$ can be zero or one. ...
2 votes
1 answer
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Characterising a set of outcomes containing the collection of pure strategy Nash equilibria

Consider a game with $N$ players, each indexed by $i=1,...,N$. Every player $i$ has to choose a $J\times 1$ vector of actions $a_i\equiv (a_{i,1},...,a_{i,J})$ where each $a_{i,j}$ can be zero or one. ...
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Cournot nash equilibrium

The market demand for a good is described by the inverse demand function $P(Q) = 120 - Q $ where $Q$ is total quantity demanded and $P(Q)$ the market price. Two firms $i =1,2$ have identical cost ...
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Pure Nash equilibrium in bidding game?

According to the answer key for a problem set, there is no pure strategy Nash equilibrium in the following problem. Yet I can't see why not. Could it be an error in the answer key? Here's the problem: ...
4 votes
2 answers
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Showing existence of a Nash equilibrium in pure strategy

Consider a game with $N$ players, each indexed by $i=1,...,N$. Every player $i$ has to choose a $J\times 1$ vector of actions $a_i\equiv (a_{i,1},...,a_{i,J})$ where each $a_{i,j}$ can be zero or one. ...
13 votes
2 answers
1k views

Rosen's Diagonal Strict Concavity condition

Consider a game with $n$ players, with strategy space $S \subset \mathbb{R}$, where $S$ is bounded set, and player's $i$ payoff function $\pi_i:S^n \rightarrow \mathbb{R}$. Rosen's condition (J. B. ...
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Find all of the Pure and Mixed Strategy Nash Equilibria [closed]

When I do the basic calculations for mixed probability, I get that the Column player always plays B. However, I am getting a negative probability for the row. Any help is appreciated.
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1 answer
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Pure Nash Equilibria 3 players game

I'm trying to solve this pure-strategy Nash equilibria of this game below: I highlighted the best pay off for player 1 and 2. But I don't get it when it comes to player 3. The correct answer is (A) ...
1 vote
1 answer
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How would a 2D model of Hotelling's law outweigh the benefits of a 1D model?

I'm not sure if this goes here, or on a math exchange. I could move it if you guys want... Let's examine Hotelling's law on a 1D plain with two shops. Both shops would do society a favour if placed ...
2 votes
1 answer
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Find value of $\beta$ for which there is a strictly dominant strategy

The question is as such: $N$ firms are lobbying for subsidies. Let $h_i$ be the number of hours spent by form $i$ for lobbying, with cost $wh_i^2$ where $w$ is a fixed constant. The subsidies granted ...

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