Phases of string stars in the presence of a spatial circle

Abstract In string theory, black holes are expected to transition into string stars as their Hawking temperatures approach the Hagedorn temperature. We study string stars and their phase transitions in the Euclidean spacetime ℝ d × S τ 1 $$ {\mathbbm{S}}_{\tau}^1 $$ × S z 1 $$ {\mathbbm{S}}_z^1 $$ ....

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Main Author: Jinwei Chu
Format: Article
Language:English
Published: SpringerOpen 2025-07-01
Series:Journal of High Energy Physics
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Online Access:https://doi.org/10.1007/JHEP07(2025)080
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author Jinwei Chu
author_facet Jinwei Chu
author_sort Jinwei Chu
collection DOAJ
description Abstract In string theory, black holes are expected to transition into string stars as their Hawking temperatures approach the Hagedorn temperature. We study string stars and their phase transitions in the Euclidean spacetime ℝ d × S τ 1 $$ {\mathbbm{S}}_{\tau}^1 $$ × S z 1 $$ {\mathbbm{S}}_z^1 $$ . Using the Horowitz-Polchinski (HP) effective field theory, we discover novel solutions for d = 2. The uniform string star exhibits a scaling symmetry that results in the absence of a critical point for its transition into the non-uniform solution. For d = 4, we show that quartic corrections to the effective action resolve the mass degeneracy of uniform string stars. At d = 5, we find that as non-uniformity increases, the quartic terms become significant (while higher-order terms remain negligible) and reverse the direction of temperature variation, leading to a swallowtail-type phase diagram in the canonical ensemble. Extending the quartic-corrected EFT to d = 6, we find that string stars with small non-uniformity dominate the microcanonical ensemble but not the canonical ensemble, similar to the d = 5 case. However, in the microcanonical ensemble, the uniform string star is anomalously (un)stable when the spatial circle is larger (smaller) than the critical size.
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spelling doaj-art-e9474d20ae6f4bc1b931feebffb71f712025-08-20T04:01:47ZengSpringerOpenJournal of High Energy Physics1029-84792025-07-012025712510.1007/JHEP07(2025)080Phases of string stars in the presence of a spatial circleJinwei Chu0Department of Physics, University of ChicagoAbstract In string theory, black holes are expected to transition into string stars as their Hawking temperatures approach the Hagedorn temperature. We study string stars and their phase transitions in the Euclidean spacetime ℝ d × S τ 1 $$ {\mathbbm{S}}_{\tau}^1 $$ × S z 1 $$ {\mathbbm{S}}_z^1 $$ . Using the Horowitz-Polchinski (HP) effective field theory, we discover novel solutions for d = 2. The uniform string star exhibits a scaling symmetry that results in the absence of a critical point for its transition into the non-uniform solution. For d = 4, we show that quartic corrections to the effective action resolve the mass degeneracy of uniform string stars. At d = 5, we find that as non-uniformity increases, the quartic terms become significant (while higher-order terms remain negligible) and reverse the direction of temperature variation, leading to a swallowtail-type phase diagram in the canonical ensemble. Extending the quartic-corrected EFT to d = 6, we find that string stars with small non-uniformity dominate the microcanonical ensemble but not the canonical ensemble, similar to the d = 5 case. However, in the microcanonical ensemble, the uniform string star is anomalously (un)stable when the spatial circle is larger (smaller) than the critical size.https://doi.org/10.1007/JHEP07(2025)080Black Holes in String TheoryBlack Holes
spellingShingle Jinwei Chu
Phases of string stars in the presence of a spatial circle
Journal of High Energy Physics
Black Holes in String Theory
Black Holes
title Phases of string stars in the presence of a spatial circle
title_full Phases of string stars in the presence of a spatial circle
title_fullStr Phases of string stars in the presence of a spatial circle
title_full_unstemmed Phases of string stars in the presence of a spatial circle
title_short Phases of string stars in the presence of a spatial circle
title_sort phases of string stars in the presence of a spatial circle
topic Black Holes in String Theory
Black Holes
url https://doi.org/10.1007/JHEP07(2025)080
work_keys_str_mv AT jinweichu phasesofstringstarsinthepresenceofaspatialcircle