Tropes in Physics

image credit

This article is not about literary tropes nor about tropes mentioned in the context of computer software. This article is about the concept of tropes discussed in philosophy and physics.

The SEP article titled “Tropes” [1] is very detailed and explains the history of this philosophical perspective. Another SEP article titled “Nominalism in Metaphysics” [2] draws our attention to the difference between “instantiation of a universal” vs. “possessing a trope“.

“…A popular nominalist theory of properties is so-called Trope Theory, which has been held by Donald Williams (1953), Keith Campbell (1990), and Douglas Ehring (2011) among others. Trope theory does not reject the existence of properties, but takes properties to be certain entities usually called ‘tropes’. Tropes are particulars, in the same sense in which individual people and individual apples are particulars. Thus when there is a scarlet apple the scarletness of the apple is not a universal but a particular scarletness, the scarletness of this apple, which exists exactly where and when this apple is scarlet. Such a particular scarletness is a trope. The apple is scarlet not in virtue of instantiating a universal but in virtue of possessing a scarlet trope.” – SEP [2]

Matteo Morganti wrote an interesting paper [3] that looks at quantum theory and the Standard Model of elementary particles and examines whether the tropes ontology favors the “particle is real” view or the “field is real” view. He concludes that:

“…complexity of fields seems incompatible with the simplicity that appears to be a necessary feature of fundamental tropes; and Simons’ proposal based on particles has been taken to be preferable.” – Matteo Morganti [3]

Morganti suggests that the fundamental tropes are: electric charge, color charge, mass and spin. He has a caveat on the “spin”.

“I therefore argue that the fundamental components of reality are a set of colour tropes, a set of mass tropes, a set of electric charge tropes, and a set of (dispositional) spin properties, to be defined on the basis of the empirically detected properties of elementary particles, as they are represented in the Standard Model.” – Matteo Morganti [3]

I was curious about the “tropes” concept because I see similarities to the concept of ‘cognitive cores’ I am developing.

In my conceptualization scheme, the ‘cognitive core’ category (electric charge, color charge, mass, spin magnitude, conservation laws) is the primary explanatory factor category and the remaining explanatory factors constitute the ‘interaction’ category.

The ‘cognitive core’ category consists of time-independent attributes whereas the ‘interaction’ category consists of time-dependent phenomena. Conservation laws, being time-independent, should be considered as part of the ‘cognitive core’ category. The dynamical (rate-dependent, time-dependent) laws should be in the ‘interaction’ category.

Any explanation of change (evolution) requires both: cognitive cores and various interactions among them. As a matter of fact, cognitive cores cannot exist without interaction.

My reservation about the “tropes” concept centers around the explanation of interactions using tropes. Morganti explains that the tropes (electric charge, color charge, mass, spin magnitude) with appropriate values characterize the force carrying particles as well. But, I think that the ‘interaction’ category is more than just force carrying particles (photon, gluon, W, Z). Tropes ontology does not say anything about the rate-dependent dynamical laws.

What is the similarity between cognitive cores and tropes? Note that I am saying “cores” (plural). Cognitive cores (plural) are particulars just like tropes are particulars. The set (electric charge, color charge, mass, spin magnitude, conservation laws) may define the ‘cognitive core’ category but there are multiple (individual) cognitive cores representing various states of the ‘cognitive core’ category.

What are the differences? The ‘cognitive core’ category includes the conservation laws and the ‘interaction’ category includes the dynamical laws. In the “tropes” ontology the “laws” are not discussed.

Am I saying anything new?

Dividing physics into 2 categories is not necessarily progress. This is not an arbitrary division, however. The ‘cognitive core’ and the ‘interaction’ categories are ontologically distinct.

What about the space invariance of cognitive cores?

Previously I said that the distinguishing characteristic between the ‘cognitive core’ and the ‘interaction’ categories is the time-dependence. All time-independent (intrinsic) properties and (conservation) laws are in the ‘cognitive core’ category and the rest of the explanatory factors are in the ‘interaction’ category.

Consider the electron cognitive core: (electric charge=-1, color charge=0, mass=0.511 MeV, spin magnitude=1/2, conservations laws applicable to electron). This set of values remains constant in time as well in space.

An individual cognitive core is invariant over space and time. All space and time dependence should be included in the ‘interaction’ category.

Category mistake

I see a fundamental difficulty in all approaches that introduce extra spatial dimensions to explain charge, mass and spin of elementary particles.

For example, Supersymmetry tries to incorporate spin into the definition of space. Another example is String Theory which is based on the premise that string dynamics – with the help of extra spatial dimensions – can explain everything about elementary particles.

Supersymmetry and String Theory make a category mistake: they mix the ‘cognitive core’ and the ‘interaction’ categories. Intrinsic properties of elementary particles are independent of space and time therefore they cannot be explained in terms of space and time.

So far there is no experimental evidence for any proposal that tries to explain intrinsic properties using extra spatial dimensions.

I hope to write more on this category mistake in the near future.


[1] SEP article titled “Tropes

[2] SEP article titled “Nominalism in Metaphysics

[3] Matteo Morganti, “Tropes and Physics”, Grazer Philosophische Studien 78 (2009), 185–205. Also found here.

This entry was posted in metaphysics, philosophy, physics and tagged . Bookmark the permalink.