With central densities as high as 5-10 times the nuclear saturation density, neutron stars exhibit extreme conditions that cannot be observed elsewhere. They are ideal astrophysical laboratories for probing the composition and properties of cold, ultra-dense matter. We shall discuss taking into account currently available data from observation, how to reveal possible sharp phase transitions in dense neutron star cores.

1.
P.
Demorest
,
T.
Pennucci
,
S.
Ransom
,
M.
Roberts
, and
J.
Hessels
,
Nature
467
,
1081
1083
(
2010
), arXiv:1010.5788 [astro-ph.HE].
2.
J.
Antoniadis
,
P. C.
Freire
,
N.
Wex
,
T. M.
Tauris
,
R. S.
Lynch
, et al,
Science
340
, p.
6131
(
2013
), arXiv:1304.6875 [astro-ph.HE].
3.
B. P.
Abbott
 et al (
Virgo, LIGO Scientific
),
Phys. Rev. Lett.
119
, p.
161101
(
2017
), arXiv:1710.05832 [gr-qc].
4.
R. C.
Tolman
,
Phys. Rev.
55
,
364
373
(
1939
).
5.
J. R.
Oppenheimer
and
G. M.
Volkoff
,
Phys. Rev.
55
,
374
381
(
1939
).
6.
K.
Hebeler
,
J. M.
Lattimer
,
C. J.
Pethick
, and
A.
Schwenk
,
Phys. Rev. Lett.
105
, p.
161102
(
2010
), arXiv:1007.1746 [nucl-th].
7.
S.
Gandolfi
,
J.
Carlson
, and
S.
Reddy
,
Phys. Rev. C
85
, p.
032801
(
2012
), arXiv:1101.1921 [nucl-th].
8.
K.
Masuda
,
T.
Hatsuda
, and
T.
Takatsuka
,
PTEP
2013
, p.
073D01
(
2013
), arXiv:1212.6803 [nucl-th].
9.
K.
Fukushima
and
T.
Kojo
,
Astrophys. J.
817
, p.
180
(
2016
), arXiv:1509.00356 [nucl-th].
10.
G.
Baym
,
T.
Hatsuda
,
T.
Kojo
,
p. D.
Powell
,
Y.
Song
, and
T.
Takatsuka
,
Rept. Prog. Phys.
81
, p.
056902
(
2018
), arXiv:1707.04966 [astro-ph.HE].
11.
L.
McLerran
and
S.
Reddy
,
Phys. Rev. Lett.
122
, p.
122701
(
2019
), arXiv:1811.12503 [nucl-th].
12.
S.
Borsanyi
,
G.
Endrodi
,
Z.
Fodor
,
S. D.
Katz
,
S.
Krieg
,
C.
Ratti
, and
K. K.
Szabo
,
JHEP
08
, p.
053
(
2012
), arXiv:1204.6710 [hep-lat].
13.
A.
Kurkela
,
E. S.
Fraga
,
J.
Schaffner-Bielich
, and
A.
Vuorinen
,
Astrophys. J.
789
, p.
127
(
2014
), arXiv:1402.6618 [astro-ph.HE].
14.
P. F.
Bedaque
and
A. W.
Steiner
,
Phys. Rev. Lett.
114
, p.
031103
(
2015
), arXiv:1408.5116 [nucl-th].
15.
M. G.
Alford
,
S.
Han
, and
M.
Prakash
,
Phys. Rev. D
88
, p.
083013
(
2013
), arXiv:1302.4732 [astro-ph.SR].
16.
M. G.
Alford
and
S.
Han
,
Eur. Phys. J.
A52
, p.
62
(
2016
), arXiv:1508.01261 [nucl-th].
17.
L.
Wade
,
J. D. E.
Creighton
,
E.
Ochsner
,
B. D.
Lackey
,
B. F.
Farr
,
T. B.
Littenberg
, and
V.
Raymond
,
Phys. Rev. D
89
, p.
103012
(
2014
), arXiv:1402.5156 [gr-qc].
18.
T.
Gross-Boelting
,
C.
Fuchs
, and
A.
Faessler
,
Nucl. Phys.
A648
,
105
137
(
1999
), arXiv:nucl-th/9810071 [nucl-th].
19.
H. T.
Cromartie
 et al, (
2019
), arXiv:1904.06759 [astro-ph.HE].
20.
S.
Han
and
A. W.
Steiner
, arXiv e-prints (
2018
), arXiv:1810.10967 [nucl-th].
21.
M. G.
Alford
and
A.
Sedrakian
,
Phys. Rev. Lett.
119
, p.
161104
(
2017
), arXiv:1706.01592 [astro-ph.HE].
22.
B. P.
Abbott
 et al (
LIGO Scientific, Virgo
),
Phys. Rev. X
9
, p.
011001
(
2019
), arXiv:1805.11579 [gr-qc].
23.
K.
Yagi
and
N.
Yunes
,
Phys. Rev. D
88
, p.
023009
(
2013
), arXiv:1303.1528 [gr-qc].
24.
K.
Yagi
and
N.
Yunes
,
Phys. Rept.
681
,
1
72
(
2017
), arXiv:1608.02582 [gr-qc].
25.
A. W.
Steiner
,
M.
Prakash
,
J. M.
Lattimer
, and
P. J.
Ellis
,
Phys. Rept.
411
,
325
375
(
2005
), arXiv:nucl-th/0410066 [nucl-th].
26.
D.
Page
,
J. M.
Lattimer
,
M.
Prakash
, and
A. W.
Steiner
, (
2013
), arXiv:1302.6626 [astro-ph.HE].
27.
E. F.
Brown
,
A.
Cumming
,
F. J.
Fattoyev
,
C. J.
Horowitz
,
D.
Page
, and
S.
Reddy
,
Phys. Rev. Lett.
120
, p.
182701
(
2018
), arXiv:1801.00041 [astro-ph.HE].
28.
C. O.
Heinke
 et al,
Astrophys. J.
714
,
894
903
(
2010
), arXiv:0911.0444 [astro-ph.HE].
29.
R.
Wijnands
,
N.
Degenaar
, and
D.
Page
,
J. Astrophys. Astron.
38
, p.
49
(
2017
), arXiv:1709.07034 [astro-ph.HE].
30.
S. M.
Morsink
and
D. A.
Leahy
,
Astrophys. J.
726
, p.
56
(
2011
), arXiv:0911.0887 [astro-ph.HE].
31.
S.
Han
and
A. W.
Steiner
,
Phys. Rev. C
96
, p.
035802
(
2017
), arXiv:1702.08452 [astro-ph.HE].
32.
N.
Andersson
and
K. D.
Kokkotas
,
Int. J. Mod. Phys.
D10
,
381
442
(
2001
), arXiv:gr-qc/0010102 [gr-qc].
33.
B.
Haskell
,
Int. J. Mod. Phys.
E24
, p.
1541007
(
2015
), arXiv:1509.04370 [astro-ph.HE].
34.
K. D.
Kokkotas
and
K.
Schwenzer
,
Eur. Phys. J.
A52
, p.
38
(
2016
), arXiv:1510.07051 [gr-qc].
35.
S.
Mahmoodifar
and
T.
Strohmayer
,
Astrophys. J.
773
, p.
140
(
2013
), arXiv:1302.1204 [astro-ph.HE].
36.
S.
Mahmoodifar
and
T.
Strohmayer
,
Astrophys. J.
840
, p.
94
(
2017
), arXiv:1705.06780 [astro-ph.HE].
37.
B.
Haskell
,
K.
Glampedakis
, and
N.
Andersson
,
Mon. Not. Roy. Astron. Soc.
441
,
1662
1668
(
2014
), arXiv:1307.0985 [astro-ph.SR].
38.
M. G.
Alford
,
S.
Han
, and
K.
Schwenzer
,
Phys. Rev. C
91
, p.
055804
(
2015
), arXiv:1404.5279 [astro-ph.SR].
39.
A. W.
Steiner
,
M.
Hempel
, and
T.
Fischer
,
Astrophys. J.
774
, p.
17
(
2013
), arXiv:1207.2184 [astro-ph.SR].
40.
J. M.
Lattimer
and
B. F.
Schutz
,
Astrophys. J.
629
,
979
984
(
2005
), arXiv:astro-ph/0411470 [astro-ph].
41.
A.
Watts
 et al,
PoS
AASKA14
, p.
043
(
2015
), arXiv:1501.00042 [astro-ph.SR].
42.
P.
Danielewicz
,
R.
Lacey
, and
W. G.
Lynch
,
Science
298
,
1592
1596
(
2002
), arXiv:nucl-th/0208016 [nucl-th].
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