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The QCD Equation of State in Small Systems

by W. A. Horowitz, Alexander Rothkopf

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Submission summary

As Contributors: William Horowitz
Arxiv Link: (pdf)
Date accepted: 2022-03-15
Date submitted: 2022-03-02 06:14
Submitted by: Horowitz, William
Submitted to: SciPost Physics Proceedings
Proceedings issue: 50th International Symposium on Multiparticle Dynamics (ISMD2021)
Academic field: Physics
  • High-Energy Physics - Theory
  • High-Energy Physics - Phenomenology
  • Nuclear Physics - Theory
Approaches: Theoretical, Phenomenological


We present first results on finite system size corrections to the equation of state, trace anomaly, and speed of sound for two model systems: 1) free, massless scalar theory and 2) quenched QCD with periodic boundary conditions (PBC). We further present work-in-progress results for quenched QCD with Dirichlet boundary conditions.

Published as SciPost Phys. Proc. 10, 025 (2022)

Author comments upon resubmission

Revised manuscript to address minor revision request from referee.

List of changes

The referee commented that:

1) "The abstract seems to start mid-paragraph! Some initial context appears to have been accidentally trimmed."

--Response: Yes! You're absolutely right. Thank you very much for catching this. Changed.

2) "In section 2, should the "phenomenologically relevant T ∼ 400 MeV" be phenomenologically *irrelevant*, since the volume is large and the finite-size effects small? This seems to be the case for the "plates" picture, but not the others, which fit the ~10% effect in the text. This part could do with some expansion to explain the relevance of the plates/tube/box labels, and the logic being used to argue T and TxL values in A+A and p+p systems: to a non-specialist like myself, this bit is interesting but opaque."

--Response: This is a nice comment, thank you. We added some sentences in the first paragraph of Section 2 expanding on the relevance for the small system size phenomenology for RHIC and LHC collisions for the more general reader

3) "It would be good to give more physics context to the trace-anomaly discussion and conclusion: what effect can this reduced coupling / increased speed of sound be expected to have on e.g. flow observables?"

--Response: This is another nice comment, thank you. We added a new second paragraph to Section 2 defining the trace anomaly in more detail and giving more insight into the phenomenological relevance of the speed of sound on flow and the extracted viscosity of the QGP fluid

Submission & Refereeing History

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Resubmission 2109.01422v2 on 2 March 2022

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