Online research in philosophy

Physicists often appeal to the beauty of a theory as a way to judge its credibility, and the most prevalent component of this beauty is symmetry. This paper describes the role and structure of symmetry arguments in physics. It demonstrates that the epistemic authority of an appeal to symmetry is based on empirical evidence and is independent of any aesthetic judgment. Furthermore, symmetry in nature is not evidence of design. Just the opposite, symmetry indicates a lack of planning. It is about nature's disregard for details.

In this paper I explore the nature of spontaneous symmetry breaking in connection with a cluster of interrelated concepts such as Curie's symmetry principle, chance, and stability.

This is the review paper for the section III ("Symmetry breaking") of the volume "Symmetries in physics: philosophical reflections", Cambridge University Press, 2003, edited by Katherine A. Brading and Elena Castellani. The paper's sections are: 1. Preliminaries (I); 2. Symmetry breaking and Curie's analysis; 3. Preliminaries (II); 4. Symmetry breaking of physical laws (4.1. Explicit symmetry breaking; 4.2. Spontaneous symmetry breaking); 5. Symmetry breaking and philosophical questions.

We pose and resolve a seeming paradox about spontaneous symmetry breaking in the quantum theory of infinite systems. For a symmetry to be spontaneously broken, it must not be implementable by a unitary operator. But Wigner's theorem guarantees that every symmetry is implemented by a unitary operator that preserves transition probabilities between pure states. We show how it is possible for a unitary operator of this sort to connect the folia of unitarily inequivalent representations. This result undermines interpretations of quantum theory that hold unitary equivalence to be necessary for physical equivalence.

Introduction Atoms theory and symmetry theory dominated physics. Symmetry propagation and interactions verify the Curie principle. But its violation by symmetry breaking is spontaneous.Fragility is creative. An information breaks a generalized symmetry. Results on symmetry breakings are not valid for fuzzy symmetries. The breaking of a fuzzy symmetry leads only to a pour symmetry (Fig.1).

Introduction Atoms theory and symmetry theory dominated physics. Symmetry propagation and interactions verify the Curie principle. But its violation by symmetry breaking is spontaneous.Fragility is creative. An information breaks a generalized symmetry. Results on symmetry breakings are not valid for fuzzy symmetries. The breaking of a fuzzy symmetry leads only to a pour symmetry (Fig.1).

This paper, part I of a two-part project, aims at answering the simple question 'what is spontaneous symmetry breaking?' by analyzing from a philosophical perspective a simple classical model. Related questions include: what does it mean to break a symmetry spontaneously? Is the breaking causal, or is the symmetry not broken but merely hidden? Is the meta-principle, 'no asymmetry in, no asymmetry out,' violated? And what is the role in this of random perturbations (or fluctuations)?

Spontaneously broken symmetries are often called hidden or secret symmetries. They are symmetries in the laws of nature that do not show up in observable phenomena. This raises the basic epistemological question: Is there reason to believe that these hidden symmetries are real features of nature rather than artifacts of theorizing. This paper clarifies the epistemic status of spontaneously broken symmetries. It presents the details of an argument by analogy that suggests the spontaneously broken gauge symmetry of electroweak interactions, and the subsequent hypothetico-deductive testing of the hypothesis. It is a story of how dubious means can lead to a credible end.

This paper aims at answering the simple question `what is spontaneous symmetry breaking (SSB)?` by analyzing from a philosophical perspective a simple classical model which exhibits all the requisite properties of SSB. Related questions include: what does it mean to say that a symmetry is spontaneously broken? Is it broken without any cause, or is the symmetry not broken but merely hidden? Is the meta-principle, `no asymmetry in, no asymmetry out,` violated by SSB? And what is the role in this of random perturbations (or fluctuations)?

This paper aims at answering the simple question, “What is spontaneous symmetry breaking (SSB) in classical systems?” I attempt to do this by analyzing from a philosophical perspective a simple classical model which exhibits some of the main features of SSB. Related questions include: What does it mean to say that a symmetry is spontaneously broken? Is it broken without any causes, or is the symmetry not broken but merely hidden? Is the principle, “no asymmetry in, no asymmetry out,” violated by SSB? What really distinguishes SSB from the usual types of symmetry breaking?