Holographic quark-hadron continuity K. Bitaghsir Fadafan, F. - PowerPoint PPT Presentation

Southampton, Mar 19, 2019 1 Andreas Schmitt Mathematical Sciences and STAG Research Centre University of Southampton Southampton SO17 1BJ, United Kingdom Holographic quark-hadron continuity K. Bitaghsir Fadafan, F. Kazemian, A. Schmitt, 1811.08698 [hep-ph] • theoretical challenges in dense QCD and relevance for neutron stars • can holographic help?

Southampton, Mar 19, 2019 2 Dense QCD: theoretical approaches T Quark − Gluon Plasma lattice QCD Hadrons pQCD Nuclear Quark Matter Matte r µ nuclear physics • lattice QCD: sign problem at nonzero µ (some recent progress) • perturbative QCD: restricted to ultra-high densities • “standard” nuclear physics: restricted to densities ≲ nuclear saturation density n 0

Southampton, Mar 19, 2019 2 Dense QCD: theoretical approaches T Quark − Gluon Plasma lattice QCD Hadrons neutron stars pQCD Nuclear Quark Matter Matte r µ nuclear physics • lattice QCD: sign problem at nonzero µ (some recent progress) • perturbative QCD: restricted to ultra-high densities • “standard” nuclear physics: restricted to densities ≲ nuclear saturation density n 0

Southampton, Mar 19, 2019 3 Quark-hadron continuity at high density? order parameter Polyakov loop (confinement) chiral condensate spontaneously breaks SU ( N f ) × SU ( N f ) Z N c symmetry exact for pure Yang-Mills ( m q = ∞ ) chiral limit ( m q = 0) → no qualitative difference between hadronic and quark matter (ignoring Cooper pairing for now) T • crossover at T = 0? quarks & gluons • quark matter in core 150 MeV of compact star? sharp interface? hadrons quark-hadron mixed phase? μ

Southampton, Mar 19, 2019 3 Quark-hadron continuity at high density? order parameter Polyakov loop (confinement) chiral condensate spontaneously breaks SU ( N f ) × SU ( N f ) Z N c symmetry exact for pure Yang-Mills ( m q = ∞ ) chiral limit ( m q = 0) → no qualitative difference between hadronic and quark matter (ignoring Cooper pairing for now) T • crossover at T = 0? quarks & gluons • quark matter in core 150 MeV of compact star? sharp interface? hadrons quark-hadron mixed phase? μ

Southampton, Mar 19, 2019 3 Quark-hadron continuity at high density? order parameter Polyakov loop (confinement) chiral condensate spontaneously breaks SU ( N f ) × SU ( N f ) Z N c symmetry exact for pure Yang-Mills ( m q = ∞ ) chiral limit ( m q = 0) → no qualitative difference between hadronic and quark matter (ignoring Cooper pairing for now) T • crossover at T = 0? quarks & gluons • quark matter in core 150 MeV of compact star? sharp interface? hadrons quark-hadron mixed phase? μ

Southampton, Mar 19, 2019 4 Observable consequences of first-order transition? • qualitative difference in mass/radius curve M. G. Alford, S. Han and M. Prakash, trans M PRD 88, 083013 (2013) ∆ε ε • sequential 1st-order R transitions? M. G. Alford and A. Sedrakian, PRL 119, 161104 (2017) ε trans p trans • different gravitational wave signal in neutron star mergers? E. R. Most et al. , PRL 122, 061101 (2019) • gravitational wave from bubble nucleation during supernova? G. Cao and S. Lin, arXiv:1810.00528 [nucl-th]

Southampton, Mar 19, 2019 5 Can holography help? • dual of QCD: probably exists, but currently out of reach • reliable strong-coupling calculation (usually infinite coupling) • successful (qualitative) predictions for heavy-ion collisions (supersymmetric YM plasma instead of quark-gluon plasma) • Sakai-Sugimoto model E. Witten, Adv. Theor. Math. Phys. 2, 505 (1998) T. Sakai and S. Sugimoto, Prog. Theor. Phys. 113, 843 (2005) – top-down approach with only 3 parameters – dual to large- N c QCD, however in inaccessible limit – successfully applied to meson, baryon, glueball spectra

Southampton, Mar 19, 2019 6 Phases in the Sakai-Sugimoto model • baryons in Sakai-Sugimoto: SU ( N f ) instantons of gauge theory on D8 branes • approximate instanton interaction from exact flat-space 2-instanton solution K. Bitaghsir Fadafan, F. Kazemian, A. Schmitt, 1811.08698 [hep-ph] chiral symmetry broken chirally symmetric x 4 u u D8 D8 instantons u c mesonic phase nuclear matter quark matter • fit 5 parameters to properties of nuclear matter at saturation density

Southampton, Mar 19, 2019 7 Holographic quark-hadron continuity? x 4 Ω μ L u ∞ u u c u T chirally broken "mesonic phase" Z = - ∞ Z = + ∞ Z chirally broken "nuclear matter" D8 D8 chirally symmetric "quark matter"

Southampton, Mar 19, 2019 8 Speed of sound Neutron stars Causality: c 2 S < 1 1 sound speed ↔ stiffness of matter c 2 � (b) 2 / 3 � ↔ neutron star masses S c 2 schematic plot from I. Tews et al. , Conformal limit 1 / 3 Neutron matter Astrophys. J. 860, 149 (2018) (a) Perturbative QCD 0 0 1 2 3 4 5 50 100 150 n [ n 0 ] 0.5 • Sakai-Sugimoto: non-monotonic 0.4 speed of sound 0.3 K. Bitaghsir Fadafan, F. Kazemian, A. 2 c s 0.2 Schmitt, 1811.08698 [hep-ph] 0.1 • see also: quarkyonic speed of sound L. McLerran, S. Reddy, 1811.12503 [nucl-th] 0.0 10 4 10 6 1 100 n / n 0

Southampton, Mar 19, 2019 9 Summary • location and nature of the quark-hadron transition at large baryon densities is unknown (sign problem) • Sakai-Sugimoto model allows for consistent treatment of nuclear and quark matter • if instanton interactions are included, nuclear and quark matter phases are continuously connected

Southampton, Mar 19, 2019 10 Outlook • include nonzero quark masses worldsheet instantons K. Hashimoto et al. , JHEP 0807, 089 (2008) • isospin asymmetry → from symmetric nuclear matter to neutron star matter • equation of state → neutron star mass/radius, deformability holographic quark matter C. Hoyos, et al. , PRL 117, 032501 (2016) N. Jokela, M. J¨ arvinen and J. Remes, arXiv:1809.07770 [hep-ph]