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Physlib.Particles.StandardModel.HiggsBoson.Potential

The potential of the Higgs field

We define the potential of the Higgs field.

We show that the potential is a smooth function on spacetime.

The Higgs potential

Basic properties

The discriminant

Boundedness of the potential

Minimum and maximum

32 declarations

definition

Higgs potential function V(ϕ,x)V(\phi, x)

For a given Higgs potential PP characterized by the mass squared parameter μ2\mu^2 and the quartic coupling coefficient λ\lambda, the function evaluates a Higgs field ϕ\phi at a point xx in spacetime as: V(ϕ,x)=μ2ϕ(x)2+λ(ϕ(x)2)2 V(\phi, x) = -\mu^2 \|\phi(x)\|^2 + \lambda (\|\phi(x)\|^2)^2 where ϕ(x)2\|\phi(x)\|^2 is the pointwise squared norm of the Higgs field at the point xx.

theorem

The Higgs Potential Function V(ϕ,x)V(\phi, x) is Smooth

For a given Higgs potential PP and a Higgs field ϕ\phi, the function mapping each point xx in spacetime to the potential value V(ϕ,x)=μ2ϕ(x)2+λ(ϕ(x)2)2V(\phi, x) = -\mu^2 \|\phi(x)\|^2 + \lambda (\|\phi(x)\|^2)^2 is smooth (CC^\infty). Here, ϕ(x)2\|\phi(x)\|^2 denotes the pointwise squared norm of the Higgs field at xx.

definition

Negation of a Higgs potential PP

Given a Higgs potential PP with mass squared coefficient μ2\mu^2 and quartic coupling coefficient λ\lambda, its negation is a new potential defined by replacing these parameters with μ2-\mu^2 and λ-\lambda respectively.

theorem

VPneg(ϕ,x)=VP(ϕ,x)V_{P_{\text{neg}}}(\phi, x) = -V_P(\phi, x)

For any Higgs potential PP, Higgs field ϕ\phi, and point xx in spacetime, the value of the negated potential PnegP_{\text{neg}} (defined by replacing the mass squared coefficient μ2\mu^2 with μ2-\mu^2 and the quartic coupling λ\lambda with λ-\lambda) evaluated at xx is equal to the negative of the value of the original potential PP. That is, VPneg(ϕ,x)=VP(ϕ,x) V_{P_{\text{neg}}}(\phi, x) = -V_P(\phi, x) where VP(ϕ,x)=μ2ϕ(x)2+λ(ϕ(x)2)2V_P(\phi, x) = -\mu^2 \|\phi(x)\|^2 + \lambda (\|\phi(x)\|^2)^2.

theorem

The mass squared coefficient of PnegP_{\text{neg}} is μ2-\mu^2

Given a Higgs potential PP with mass squared coefficient μ2\mu^2, the mass squared coefficient of its negation PnegP_{\text{neg}} is equal to μ2-\mu^2.

theorem

The quartic coupling of PnegP_{\text{neg}} is λ-\lambda

Let PP be a Higgs potential with quartic coupling coefficient λ\lambda. The quartic coupling coefficient of its negation PnegP_{\text{neg}} is equal to λ-\lambda.

theorem

V(0,x)=0V(0, x) = 0 for Higgs potential VV

For any point xx in spacetime, the Higgs potential V(ϕ,x)V(\phi, x) evaluated at the zero Higgs field ϕ=0\phi = 0 is zero, i.e., V(0,x)=0V(0, x) = 0.

theorem

Completion of the square for the Higgs potential V(ϕ,x)V(\phi, x)

Let PP be a Higgs potential characterized by the mass squared parameter μ2\mu^2 and the quartic coupling coefficient λ\lambda. For any Higgs field ϕ\phi and any point xx in spacetime, if λ0\lambda \neq 0, the Higgs potential V(ϕ,x)V(\phi, x) satisfies the completed square identity: V(ϕ,x)=λ(ϕ(x)2μ22λ)2(μ2)24λ V(\phi, x) = \lambda \left( \|\phi(x)\|^2 - \frac{\mu^2}{2\lambda} \right)^2 - \frac{(\mu^2)^2}{4\lambda} where ϕ(x)2\|\phi(x)\|^2 is the pointwise squared norm of the Higgs field at xx.

theorem

λ(ϕ(x)2)2μ2ϕ(x)2V(ϕ,x)=0\lambda (\|\phi(x)\|^2)^2 - \mu^2 \|\phi(x)\|^2 - V(\phi, x) = 0

For a Higgs field ϕ\phi and a point xx in spacetime, let ϕ(x)2\|\phi(x)\|^2 denote the pointwise squared norm of the field, and let V(ϕ,x)V(\phi, x) be the Higgs potential characterized by the mass squared parameter μ2\mu^2 and the quartic coupling coefficient λ\lambda. These quantities satisfy the following quadratic equation: λ(ϕ(x)2)2μ2ϕ(x)2V(ϕ,x)=0 \lambda (\|\phi(x)\|^2)^2 - \mu^2 \|\phi(x)\|^2 - V(\phi, x) = 0

theorem

V(ϕ,x)=0V(\phi, x) = 0 if and only if ϕ(x)=0\phi(x) = 0 or ϕ(x)2=μ2/λ\|\phi(x)\|^2 = \mu^2 / \lambda

Let PP be a Higgs potential characterized by the mass squared parameter μ2\mu^2 and the quartic coupling coefficient λ\lambda. For any Higgs field ϕ\phi and any point xx in spacetime, assuming λ0\lambda \neq 0, the Higgs potential V(ϕ,x)V(\phi, x) is zero if and only if the value of the Higgs field at xx is zero (ϕ(x)=0\phi(x) = 0) or the squared norm of the field at that point satisfies ϕ(x)2=μ2λ\|\phi(x)\|^2 = \frac{\mu^2}{\lambda}.

definition

Quadratic discriminant of the Higgs potential Δ(ϕ,x)\Delta(\phi, x)

The discriminant of the quadratic equation associated with the Higgs potential for a Higgs field ϕ\phi at a spacetime point xx. Given the potential V(ϕ,x)=λ(ϕ(x)2)2μ2ϕ(x)2V(\phi, x) = \lambda (\|\phi(x)\|^2)^2 - \mu^2 \|\phi(x)\|^2, this value corresponds to the discriminant of the quadratic ay2+by+c=0a y^2 + b y + c = 0 where y=ϕ(x)2y = \|\phi(x)\|^2, a=λa = \lambda, b=μ2b = -\mu^2, and c=V(ϕ,x)c = -V(\phi, x). It is given by the formula Δ=(μ2)24λ(V(ϕ,x))=μ4+4λV(ϕ,x)\Delta = (-\mu^2)^2 - 4\lambda(-V(\phi, x)) = \mu^4 + 4\lambda V(\phi, x), where μ2\mu^2 is the mass squared parameter and λ\lambda is the quartic coupling coefficient.

theorem

The quadratic discriminant of the Higgs potential Δ(ϕ,x)\Delta(\phi, x) is non-negative

For any Higgs field ϕ\phi and any point xx in spacetime, let V(ϕ,x)=λ(ϕ(x)2)2μ2ϕ(x)2V(\phi, x) = \lambda (\|\phi(x)\|^2)^2 - \mu^2 \|\phi(x)\|^2 be the Higgs potential with quartic coupling coefficient λ\lambda and mass squared parameter μ2\mu^2. If λ0\lambda \neq 0, then the discriminant of the associated quadratic equation, defined as Δ(ϕ,x)=μ4+4λV(ϕ,x)\Delta(\phi, x) = \mu^4 + 4\lambda V(\phi, x), is non-negative, i.e., 0Δ(ϕ,x)0 \leq \Delta(\phi, x).

theorem

Δ(ϕ,x)=Δ(ϕ,x)Δ(ϕ,x)\Delta(\phi, x) = \sqrt{\Delta(\phi, x)} \cdot \sqrt{\Delta(\phi, x)}

Let PP be a Higgs potential characterized by a quartic coupling coefficient λ0\lambda \neq 0 and a mass squared parameter μ2\mu^2. For any Higgs field ϕ\phi and any point xx in spacetime, the associated quadratic discriminant Δ(ϕ,x)=μ4+4λV(ϕ,x)\Delta(\phi, x) = \mu^4 + 4\lambda V(\phi, x) is equal to the product of its square root with itself: Δ(ϕ,x)=Δ(ϕ,x)Δ(ϕ,x). \Delta(\phi, x) = \sqrt{\Delta(\phi, x)} \cdot \sqrt{\Delta(\phi, x)}.

theorem

Δ(ϕ,x)=0    V(ϕ,x)=(μ2)24λ\Delta(\phi, x) = 0 \iff V(\phi, x) = -\frac{(\mu^2)^2}{4\lambda}

Let PP be a Higgs potential characterized by a quartic coupling coefficient λ0\lambda \neq 0 and a mass squared parameter μ2\mu^2. For any Higgs field ϕ\phi and any point xx in spacetime, the quadratic discriminant Δ(ϕ,x)\Delta(\phi, x) associated with the potential is equal to zero if and only if the potential function V(ϕ,x)V(\phi, x) satisfies V(ϕ,x)=(μ2)24λ. V(\phi, x) = -\frac{(\mu^2)^2}{4\lambda}.

theorem

Δ(ϕ,x)=0    ϕ(x)2=μ22λ\Delta(\phi, x) = 0 \iff \|\phi(x)\|^2 = \frac{\mu^2}{2\lambda}

Let PP be a Higgs potential characterized by a quartic coupling coefficient λ0\lambda \neq 0 and a mass squared parameter μ2\mu^2. For any Higgs field ϕ\phi and any point xx in spacetime, the quadratic discriminant Δ(ϕ,x)\Delta(\phi, x) associated with the Higgs potential is zero if and only if the pointwise squared norm of the Higgs field ϕ(x)2\|\phi(x)\|^2 satisfies ϕ(x)2=μ22λ. \|\phi(x)\|^2 = \frac{\mu^2}{2\lambda}.

theorem

If λ<0\lambda < 0, then V(ϕ,x)(μ2)24λV(\phi, x) \leq -\frac{(\mu^2)^2}{4\lambda}

Let PP be a Higgs potential characterized by a mass squared parameter μ2\mu^2 and a quartic coupling coefficient λ\lambda. If λ<0\lambda < 0, then for any Higgs field ϕ\phi and any point xx in spacetime, the potential function V(ϕ,x)V(\phi, x) is bounded above by V(ϕ,x)(μ2)24λ. V(\phi, x) \leq -\frac{(\mu^2)^2}{4\lambda}.

theorem

If λ>0\lambda > 0, then V(ϕ,x)(μ2)24λV(\phi, x) \geq -\frac{(\mu^2)^2}{4\lambda}

Let PP be a Higgs potential characterized by a mass squared parameter μ2\mu^2 and a quartic coupling coefficient λ\lambda. If λ>0\lambda > 0, then for any Higgs field ϕ\phi and any point xx in spacetime, the potential function V(ϕ,x)V(\phi, x) is bounded below by (μ2)24λV(ϕ,x). -\frac{(\mu^2)^2}{4\lambda} \leq V(\phi, x).

theorem

If λ<0\lambda < 0 and μ2>0\mu^2 > 0, then V(ϕ,x)0V(\phi, x) \le 0

Let PP be a Higgs potential with mass squared parameter μ2\mu^2 and quartic coupling λ\lambda, such that the potential of a Higgs field ϕ\phi at a point xx in spacetime is given by V(ϕ,x)=μ2ϕ(x)2+λ(ϕ(x)2)2V(\phi, x) = -\mu^2 \|\phi(x)\|^2 + \lambda (\|\phi(x)\|^2)^2. If λ<0\lambda < 0, then for every Higgs field ϕ\phi and point xx in spacetime, if the mass squared parameter is positive (μ2>0\mu^2 > 0), then the potential is non-positive, i.e., V(ϕ,x)0V(\phi, x) \leq 0.

theorem

If λ>0\lambda > 0 and μ2<0\mu^2 < 0, then V(ϕ,x)0V(\phi, x) \ge 0

Let PP be a Higgs potential with mass squared parameter μ2\mu^2 and quartic coupling λ\lambda, such that the potential of a Higgs field ϕ\phi at a point xx in spacetime is given by V(ϕ,x)=μ2ϕ(x)2+λ(ϕ(x)2)2V(\phi, x) = -\mu^2 \|\phi(x)\|^2 + \lambda (\|\phi(x)\|^2)^2. If λ>0\lambda > 0, then for every Higgs field ϕ\phi and point xx in spacetime, if the mass squared parameter is negative (μ2<0\mu^2 < 0), the potential is non-negative, i.e., V(ϕ,x)0V(\phi, x) \geq 0.

theorem

Existence of solutions for V(ϕ,x)=cV(\phi, x) = c when λ<0\lambda < 0

Let PP be a Higgs potential with mass squared parameter μ2\mu^2 and quartic coupling λ<0\lambda < 0. For any real number cc, there exists a Higgs field ϕ\phi and a spacetime point xx such that the potential V(ϕ,x)=μ2ϕ(x)2+λ(ϕ(x)2)2V(\phi, x) = -\mu^2 \|\phi(x)\|^2 + \lambda (\|\phi(x)\|^2)^2 is equal to cc if and only if one of the following two conditions holds: - μ2>0\mu^2 > 0 and c0c \leq 0. This implies that if λ\lambda is negative and μ2\mu^2 is positive, the potential takes every non-positive value. - μ20\mu^2 \leq 0 and c(μ2)24λc \leq -\frac{(\mu^2)^2}{4\lambda}. This implies that if λ\lambda is negative and μ2\mu^2 is non-positive, the potential takes every value less than or equal to the bound (μ2)24λ-\frac{(\mu^2)^2}{4\lambda}.

theorem

Existence of solutions for V(ϕ,x)=cV(\phi, x) = c when λ>0\lambda > 0

Let PP be a Higgs potential with mass squared parameter μ2\mu^2 and quartic coupling λ>0\lambda > 0. For any real number cc, there exists a Higgs field ϕ\phi and a spacetime point xx such that the potential V(ϕ,x)=μ2ϕ(x)2+λ(ϕ(x)2)2V(\phi, x) = -\mu^2 \|\phi(x)\|^2 + \lambda (\|\phi(x)\|^2)^2 is equal to cc if and only if one of the following two conditions holds: - μ2<0\mu^2 < 0 and 0c0 \le c. This implies that if λ\lambda is positive and μ2\mu^2 is negative, the potential takes every non-negative value. - 0μ20 \le \mu^2 and (μ2)24λc-\frac{(\mu^2)^2}{4\lambda} \le c. This implies that if λ\lambda is positive and μ2\mu^2 is non-negative, the potential takes every value greater than or equal to its minimum bound (μ2)24λ-\frac{(\mu^2)^2}{4\lambda}.

definition

The Higgs potential V(ϕ,x)V(\phi, x) is bounded from below

For a given Higgs potential PP, the property P.IsBoundedP.\text{IsBounded} is true if the potential function V(ϕ,x)V(\phi, x) is bounded from below. Specifically, there exists a real constant cc such that for all Higgs fields ϕ\phi and all points xx in spacetime, the potential satisfies V(ϕ,x)cV(\phi, x) \geq c.

theorem

If the Higgs potential is bounded, then λ0\lambda \geq 0

Let PP be a Higgs potential with quartic coupling coefficient λ\lambda and mass squared parameter μ2\mu^2, defined by the function V(ϕ,x)=μ2ϕ(x)2+λ(ϕ(x)2)2V(\phi, x) = -\mu^2 \|\phi(x)\|^2 + \lambda (\|\phi(x)\|^2)^2 for a Higgs field ϕ\phi and spacetime point xx. If the potential PP is bounded from below (i.e., there exists a real constant cc such that V(ϕ,x)cV(\phi, x) \geq c for all ϕ\phi and xx), then the quartic coefficient λ\lambda is non-negative (λ0\lambda \geq 0).

theorem

If λ>0\lambda > 0, then the Higgs potential is bounded

Let PP be a Higgs potential with quartic coupling coefficient λ\lambda. If λ>0\lambda > 0, then the potential PP is bounded from below. This means there exists a real constant cc such that for any Higgs field ϕ\phi and any point xx in spacetime, the potential function satisfies V(ϕ,x)cV(\phi, x) \geq c.

definition

P is bounded    μ20P \text{ is bounded} \iff \mu^2 \le 0 when λ=0\lambda = 0

Let PP be a Higgs potential with quartic coupling λ\lambda and mass squared parameter μ2\mu^2. If the quartic coupling λ\lambda is zero, then the potential PP is bounded from below if and only if the mass squared parameter μ2\mu^2 is non-positive (μ20\mu^2 \le 0). This reflects the condition under which the term μ2ϕ2-\mu^2 \|\phi\|^2 remains bounded from below.

theorem

Condition for Global Minimum of Higgs Potential when μ20\mu^2 \le 0 and λ>0\lambda > 0

Let VV be a Higgs potential with mass squared parameter μ2\mu^2 and quartic coupling λ\lambda. If λ>0\lambda > 0 and μ20\mu^2 \le 0, then for any Higgs field ϕ\phi and spacetime point xx, the pair (ϕ,x)(\phi, x) is a global minimum of the potential function (ϕ,x)V(ϕ,x)(\phi, x) \mapsto V(\phi, x) if and only if V(ϕ,x)=0V(\phi, x) = 0.

theorem

Global Minimum of Higgs Potential     ϕ(x)=0\iff \phi(x) = 0 for μ20,λ>0\mu^2 \le 0, \lambda > 0

Let VV be a Higgs potential characterized by the mass squared parameter μ2\mu^2 and the quartic coupling λ\lambda. Suppose λ>0\lambda > 0 and μ20\mu^2 \le 0. For any Higgs field ϕ\phi and spacetime point xx, the pair (ϕ,x)(\phi, x) is a global minimum of the potential function (ϕ,x)V(ϕ,x)(\phi, x) \mapsto V(\phi, x) if and only if the Higgs field vanishes at that point, i.e., ϕ(x)=0\phi(x) = 0.

theorem

Condition for Global Minimum of the Higgs Potential for μ20\mu^2 \ge 0 and λ>0\lambda > 0

Let PP be a Higgs potential with mass squared parameter μ20\mu^2 \ge 0 and quartic coupling λ>0\lambda > 0. For any Higgs field ϕ\phi and spacetime point xx, the pair (ϕ,x)(\phi, x) is a global minimum of the potential function V(ϕ,x)V(\phi, x) if and only if V(ϕ,x)=(μ2)24λV(\phi, x) = -\frac{(\mu^2)^2}{4\lambda}.

theorem

Global minimum of the Higgs potential     ϕ(x)2=μ22λ\iff \|\phi(x)\|^2 = \frac{\mu^2}{2\lambda} for μ20\mu^2 \ge 0 and λ>0\lambda > 0

Let PP be a Higgs potential with quartic coupling λ>0\lambda > 0 and mass squared parameter μ20\mu^2 \ge 0. For any Higgs field ϕ\phi and point xx in spacetime, the pair (ϕ,x)(\phi, x) is a global minimum of the potential function V(ϕ,x)V(\phi, x) if and only if the pointwise squared norm of the Higgs field satisfies ϕ(x)2=μ22λ. \|\phi(x)\|^2 = \frac{\mu^2}{2\lambda}.

theorem

Global minimum of Higgs potential for λ>0    (0μ2ϕ(x)2=μ22λ)(μ2<0ϕ(x)=0)\lambda > 0 \iff (0 \le \mu^2 \land \|\phi(x)\|^2 = \frac{\mu^2}{2\lambda}) \lor (\mu^2 < 0 \land \phi(x) = 0)

Let PP be a Higgs potential with mass squared parameter μ2\mu^2 and quartic coupling λ\lambda. Suppose the quartic coupling is positive, λ>0\lambda > 0. For any Higgs field ϕ\phi and spacetime point xx, the configuration (ϕ,x)(\phi, x) is a global minimum of the potential function V(ϕ,x)V(\phi, x) if and only if one of the following conditions holds: 1. μ20\mu^2 \ge 0 and the squared norm of the Higgs field satisfies ϕ(x)2=μ22λ\|\phi(x)\|^2 = \frac{\mu^2}{2\lambda}. 2. μ2<0\mu^2 < 0 and the Higgs field vanishes at that point, ϕ(x)=0\phi(x) = 0.

theorem

Global maximum of VP    V_P \iff global minimum of VPnegV_{P_{\text{neg}}}

For a given Higgs potential PP, let VP(ϕ,x)V_P(\phi, x) denote the potential function evaluating a Higgs field ϕ\phi at a point xx in spacetime, defined by VP(ϕ,x)=μ2ϕ(x)2+λ(ϕ(x)2)2V_P(\phi, x) = -\mu^2 \|\phi(x)\|^2 + \lambda (\|\phi(x)\|^2)^2. Let PnegP_{\text{neg}} be the negated potential such that its value is VPneg(ϕ,x)=VP(ϕ,x)V_{P_{\text{neg}}}(\phi, x) = -V_P(\phi, x). A configuration (ϕ,x)(\phi, x) is a global maximum of the Higgs potential PP if and only if it is a global minimum of the negated potential PnegP_{\text{neg}}.

theorem

Global maximum of Higgs potential for λ<0    (μ20ϕH2=μ22λ)(μ2>0ϕ=0)\lambda < 0 \iff (\mu^2 \le 0 \land \|\phi\|_H^2 = \frac{\mu^2}{2\lambda}) \lor (\mu^2 > 0 \land \phi = 0)

Let PP be a Higgs potential with mass squared parameter μ2\mu^2 and quartic coupling λ\lambda. Suppose the quartic coupling is negative, λ<0\lambda < 0. For any Higgs field ϕ\phi and spacetime point xx, the configuration (ϕ,x)(\phi, x) is a global maximum of the potential function V(ϕ,x)V(\phi, x) if and only if one of the following conditions holds: 1. μ20\mu^2 \le 0 and the squared norm of the Higgs field satisfies ϕ(x)H2=μ22λ\|\phi(x)\|_H^2 = \frac{\mu^2}{2\lambda}. 2. μ2>0\mu^2 > 0 and the Higgs field vanishes at that point, ϕ(x)=0\phi(x) = 0.