G2 Lattice Gauge Theory at Finite Density andTemperature
Andreas Wipf
Theoretisch-Physikalisches InstitutFriedrich-Schiller-University Jena
collaboration withA. Maas, L. von Smekal, B. Wellegehausen (C. Wozar)
5th International Conference on New Frontiers in Physics , Kolymbari, July 2016
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
1 G2-Gluodynamics
2 G2 Yang-Mills-Higgs Theory and SSB
3 G2 Gauge Theory with Dynamical Fermions
4 Spectroscopy
5 Finite Temperature and DensityPhase diagram – deconfinement transitionPhase diagram – baryon numberHigh-precision simulations for two-flavor SU(2) in two dimensions
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Bjoern Wellegehausen,Jena/Gießen
Axel MaasGraz
Lorenz von Smekal,Gießen
eff. Polyakov Loop dynamicsPhys. Rev. D80 (2009) 065028
Casimir Scaling/string breakingPhys. Rev. D83 (2011) 016001
phase diagram YMHPhys. Rev. D83 (2011) 114502
phase diagram with fermions Phys. Rev. D86(2012) 111901
phase diagram, spectroscopyPhys. Rev. D89 (2014) 056007
earlier papers with C. Wozar.
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Expected QCD phase diagram 4 / 57
various condensates, quark density, Polyakov-loops, . . .almost no first principle results for large baryon density
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
In this talk: Lattice approach 5 / 57
space-time latticefinite volume
V = (aNt )× (aNs)d−1
β = aNt , L = aNs
functional integrals→finite-dimensional integralswithout quarks:accurate resultson large lattices ≈ 1284
with quarks:fermionic determinantnon-local integrandextrapolation (a,mF )sign problem for µ 6= 0
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Gluodynamics and QCD 6 / 57
zero baryon-density: accessible to simulationswithout quarks⇒weakly first order PT with order parameterMC method applicable, relatively cheapwith quarks⇒masses of hadrons, glueballs, . . . , matrix elements, life-times,equation of state, . . .expensive simulations
large baryon density: not accessible to simulationsnot much known (effective models)ideas/proposals on exotic phases of cold dense matterrelevant for n∗ (equation of state)
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Why G2-Gauge Theory 7 / 57
no sign problem⇒ simulations at finite density feasiblerepresentations are realbaryon and meson spectrum similar to QCDsimilar glueball spectrum as SU(3) Wellegehausen, Wozar, AW
G2 contains SU(3) as subgroup⇒smooth interpolation G2 −→ SU(3) by SSBconfinement↔ center of gauge group? Hollands, Minkowski, Pepe, Wiese
smallest (simply connected) Lie group with trivial center
only gauge theory with fermionic baryons whichhas been simulated at high baryon density
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Color-singlet states and branching to SU(3) 8 / 57
expected colour-singlet bound states
{7} ⊗ {7} = {1} ⊕ {7} ⊕ {14} ⊕ {27}{7} ⊗ {7} ⊗ {7} = {1} ⊕ 4 · {7} ⊕ 2 · {14} ⊕ . . .{14} ⊗ {14} = {1} ⊕ {14} ⊕ {27} ⊕ . . . ,
{14} ⊗ {14} ⊗ {14} = {1} ⊕ {7} ⊕ 5 · {14} ⊕ . . . ,{7} ⊗ {14} ⊗ {14} ⊗ {14} = {1} ⊕ . . .
SSB G2 → SU(3) (cp. GUTS)
fermions: {7} −→ {3} ⊕ {3} ⊕ {1},gauge bosons: {14} −→ {8} ⊕ {3} ⊕ {3}.
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
G2 Yang-Mills theory has 9 / 57
quark gluon plasma at high Tconfinement of color at low Tteaches us about role of center for confinementtests ideas/proposals on exotic phases of cold dense matterallows for a test quality of frequently used approximations:MF-type, hopping-parameter expansions, strong-coupling expansions,effective models, renormalization group, . . .condensates and nB distinguish between different phasessuggestions are welcome
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
G2 gauge theory without fermions: what is known 10 / 57
1st order confinement/deconfinement PT Hollands, Minkowski, Pepe, Wiese 2003
Cossu, D’Elia, di Giacomo, Lucini, Pica 2007
Casimir scaling Greensite, Langfeld, Olejnik, Reinhardt, Tok 2007; Liptak, Olejnik 2008
effective Polyakov loop dynamics Wellegehausen, AW, Wozar 2009
chiral restoration in quenched theory at same Tc Danzer, Gattringer, Maas 2009
G2 monopoles (Shnir), semiclassical dyon picture (Diakonov, Petrov 2010), . . .string breaking, gluelump spectrum Wellegehausen, AW, Wozar 2011
SSB G2 →SU(3) Wellegehausen, AW, Wozar 2012
topological properties, instantons Maas, Olejnik, Ilgenfritz 2013
equation of state, 〈Tµµ 〉T ∝ T 2
Bruno, Caselle, Panero, Pellegrini 2015
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
simulations: first order PT (local HMC, moderate 163 × 6 lattice)
rapid change with β ∝ 1/g2
histogram in vicinity of βc ≈ 9.65first order transition
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Casimir scaling 12 / 57
static quark-antiquark potential representation R
VR(R) = γR −αRR
+ σRR
e−βV (R) varies over ≈ 50 orders of magnitude until string breaksCasimir scaling hypothesis for string tensions:
σRcR
=σR′
cR′
−2
−1
0
1
2
3
4
5
6
7
0 1 2 3 4 5 6
VR/µ
µR
R = 7, β = 30, N = 483R = 14, β = 30, N = 483R = 7, β = 20, N = 323R = 14, β = 20, N = 323
(scaled) string tensions (µ2 = σ7) Liptak, Olejnik; WWW: N = 48, β = 30
aAndreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Phase diagram of finite-temperature G2 Higgs Model 13 / 57
lattice action with normalized 7-component Higgs ϕ
SYMH[U , ϕ] = −β∑2
(1− 1
7tr U2
)− κ
∑ϕT
x Ux,µϕx+µ
spontaneous symmetry breaking G2 → SU(3):{14} −→ {8} ⊕ {3} ⊕ {3} gluons ⊕ massive Vector bosonsκ = 0: pure G2 gauge theory: 1st order deconfinement transitionκ =∞: pure SU(3) gauge theory: 1st order deconfinement transitioncomplete phase diagram of G2 YMH theory:average plaquette action, Higgs action and Polyakov loopsusceptibilities (and higher derivatives), finite size analysis≤ 5× 105 configurations, on grid ≤ β = 5 . . . 10, κ = 0 . . . 104
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Phase diagram: global picture 14 / 57
βcrit = 9.55(5) , κcrit = 1.50(4)
0
100
101
102
103
∞
5 10 15 30 ∞
κ
β
SO(7) broken
SU(3) deconfinement
SO(7) unbroken
G2 deconfinement
confinement
3
456
163 × 6-lattice
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Gap in first order line? 15 / 57
00.5 6 7 8 900.5 6 7 8 9 9.39.49.59.69.79.89.9 10β
20 30 60 ∞20 30 60 ∞
11.21.41.61.82κ
101001000∞101001000∞ SO(7) brokenSU(3) de on�nement
SO(7) unbrokenG2 de on�nement on�nement
Summarizing the phase diagram of G2 YMH-theoryWellegehausen, Wozar, AW
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
G2 QCD with dynamical fermions 16 / 57
collaboration with Axel Maas, Lorenz von Smekal and Bjoern Wellegehausen
det D(U, µ,m] ≥ 0 for any Nf
⇒ simulations at finite T and µ possiblemeasure chiral/di-quark condensate, baryon-density, Polyakov loop,. . .interpretation of phase transitions and condensates⇒ need particle spectrum at T = 0 Tglueballsmesonsbaryons: nq = 1,2,3exotic particles
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
global symmetries and possible breakings for Nf = 1 17 / 57
SU(2) U(1)Bm
U(1)B U(1)Bm
µ µ
enlarged chiral symmetry (Pauli-Gürsey)Goldstone bosons
d(0++) ∼ ψCγ5ψ + ψγ5ψC and d(0+−) ∼ ψCγ5ψ − ψγ5ψ
C
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Spectroscopy – lattice setup 18 / 57
Wilson fermions, Symanzik improved gauge action, RHMC-algorithmβ = 0.96, κ = 0.159 fixedensemble for Spectroscopy16× 83 latticeProton mass mN = 938 MeV, diquark mass md(0+) = 247 MeV
Lattice spacing a = 0.343 fm ∼ (575 MeV)−1
ensembles at finite temperature and densityLattice size: Nt × 83 with Nt = 2 . . . 16T = 36 . . . 287 MeV, 9 valuesµ = 0 . . . .354 MeV, 60 values below lattice saturation
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Interpolating operators: Mesons nq = 0 19 / 57
{7} ⊗ {7} = {1} ⊕ . . .
Name Operator Pos. Spin Colour Flavour J Pη uγ5u S A S S 0 -f uu S A S S 0 +ω uγµu S S S A 1 -h uγ5γµu S S S A 1 +π uγ5d S A S S 0 -a ud S A S S 0 +ρ uγµd S S S A 1 -b uγ5γµd S S S A 1 +
unquenched or partially quenched in one-flavor simulations
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Interpolating operators: Baryons nq = 1 20 / 57
{7} ⊗ {7} ⊗ {7} = {1} ⊕ . . .{7} ⊗ {14} ⊗ {14} ⊗ {14} = {1} ⊕ . . .
Name Operator Pos. Spin Col. Flav. J PHybrid εabcdefguaF p
µνF qµνF r
µνT bcp T de
q T fgr S S A S 1/2 ±
∆ T abc(uaγµ287ub)uc S S A S 3/2 ±N T abc(uaγ5db)uc S A A A 1/2 ±
hybrid-spectroscopy difficultmη −mdiquark = disconnected contributions
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Interpolating operators: Baryons nq = 2 21 / 57
{7} ⊗ {7} = {1} ⊕ . . .
Name Operator Pos. Spin Colour Flavour J P Cd(0++) uCγ5u + uγ5uC S A S S 0 + +d(0+−) uCγ5u − uγ5uC S A S S 0 + -d(0−+) uCu + uuC S A S S 0 - +d(0−−) uCu − uuC S A S S 0 - -
d(1++) uCγµd + uγµdC S S S A 1 + +d(1+−) uCγµd − uγµdC S S S A 1 + -d(1−+) uCγ5γµd + uγ5γµdC S S S A 1 - +d(1−−) uCγ5γµd − uγ5γµdC S S S A 1 - -
diquark masses are degenerate (cc)no sources for diquarks needed
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Interpolating operators: Baryons nq = 3 22 / 57
{7} ⊗ {7} ⊗ {7} = {1} ⊕ . . .
Name Operator Pos. Spin Colour Flavour J P∆ T abc(uC
a γµub)uc S S A S 3/2 ±N T abc(uC
a γ5db)uc S A A A 1/2 ±
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Masses of mesons and baryons 23 / 57
Wellegehausen, Maas, Smekal, AW (2013)
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Low temperature: baryon density vs. chemical potential 24 / 57
silver blazediquark BEcondensationmd(0+) = 247 MeVplateaus visible forlarger nq
three transitionshadronic phase atm∆ ≈ mN
Wellegehausen, Maas, Smekal, AW (2013)
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
(Preliminary) interpretation 25 / 57
low density: in accordance with silver blazetwo small jumps at diquark thresholds⇒ two (probably) second order PT?two plateaus after thresholdsBose-condensates of diquarks?one (probably) first order PT at ≈ ∆ thresholdhadronic phase for higher nq (under investigation)aµ & 1: lattice artifacts, e.g. saturation effects
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Phase diagram – Deconfinement transition (µ = 0) 26 / 57
Polyakov loop 〈P〉 and susceptibility ∂〈P〉∂T at µ = 0
Deconfinement transition at Tc(µ = 0) ≈ 137 MeV(cubic splines, no thermalization at 80 MeV)
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Phase diagram – deconfinement transition (selected µ’s) 27 / 57
Polyakov loop 〈P〉 and susceptibility ∂〈P〉∂T
deconfinement transition shifts to smaller T for larger µpeak of susceptibility increases
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Phase diagram – deconfinement transition 28 / 57
Polyakov loop 〈P〉 and susceptibility ∂〈P〉∂T (60 µ’s)
deconfinement transition shifts to smaller T for larger µpeak of susceptibility increases, consistent with T ′c(µ)
∣∣µ=0 = 0
Tc(µ)
Tc(0)∼ 1 + 0.001(8)
µ
Tc(0)− 0.031(6)
(µ
Tc(0)
)2
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
scanning (T , µ) space 29 / 57
temperatures: T = 287, 192, 144, 115, 96, 82, 72, 48, 36 MeVchemical potential: 60 µ-values between 0 and 354 MeV for each T
100 200 300 400 500 600
50
100
150
200
250
300
00
Tin
MeV
µ in MeV
deconf
conf
vacuum
diquark
cond
nuclear
matter
underway
latticesaturation
?
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Phase diagram – baryon number 30 / 57
quark number density
T = 287 MeV
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Phase diagram – baryon number 31 / 57
quark number density
T = 192 MeV
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Phase diagram – baryon number 32 / 57
quark number density
T = 144 MeV
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Phase diagram – baryon number 33 / 57
quark number density
T = 115 MeV, µdeconf = 317 MeV
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Phase diagram – baryon number 34 / 57
quark number density
T = 96 MeV, threshold effects?
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Phase diagram – baryon number 35 / 57
quark number density
T = 82 MeV
estimater problem for small µ when 〈nB〉 ≈ 10−3 − 10−4
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Phase diagram – baryon number 36 / 57
quark number density
T = 72 MeV
〈nB〉 may jump at thresholds
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Phase diagram – baryonic matter transition 37 / 57
quark number density
T = 48 MeV
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Phase diagram – baryonic matter transition 38 / 57
quark number density
T = 36 MeV
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Simulation at higher µ and lower T required 39 / 57
G2-QCD phase diagram with V = (2.7 fm)3 and md(0+) = 247 MeV
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
High-precision model calculations: two-flavor SU(2) in two dimensions 40 / 57
4-dimensions: parameter study in (µ,T ) plane very expensiveas today low T and finite µ not accessible in 4-dimensional theoriesdetailed studies of µ-dependence for interpretation⇒ lower-dimensional theories as test-bedshere: two-flavor SU(2) in two dimensionsno sign problembehaves (not only qualitatively) similar to G2 QCDin two dimensions: no breaking of continuous symmetry!
earlier studies in 4d: Simon Hands et al., von Smekal et al.
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
no SSB of continuous symmetry, π not lightest particle,lightest particle: vector diquark (as for G2)scale: µc defined by silver blaze, µc = 1
2 md
mass of vector diquark in lattice units 0.22complete mass-spectrum: in progressSimulation parameters:
simulations at fixed β = 3.8 and κ = 0.27 and Ns = 16Nt ∈ {2, 4, 6, 8, 10, 12, 14, 16, 24, 32, 48, 128}, 12 temperaturesµ from 0 to 1.15 in steps ∆µ = 0.002, fine gridcolor-plots in T -variable interpolatedtypical 1000 configurations, HMC, Wilson fermions,
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
µ-dependence of chiral condensate for different T 42 / 57
steps are washed out at higher temperaturesvarious types of diquarks can condensevery high resolution in µ, small statistical errors
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
color-plot 〈ψψ〉, gobal picture 43 / 57
µc defined by silver blazeµ ≥ 7µc : lattice artifacts, saturation
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
color-plot 〈ψψ〉, intermediate µ 44 / 57
µ < µc : explicit breaking of chiral symmetryµ ' µc : chiral condensate rotates into diquark condensate
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
color-plot 〈ψψ〉, small µ 45 / 57
line emanating from µ = µc bends ’to the right’
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
color-plot ∂µ〈ψψ〉, small µ 46 / 57
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
T -dependence of 〈P〉, several µ 47 / 57
staggered fermions 〈P〉 = 0, not true for Wilson fermionscan probe very low temperature (not yet feasible in 4 dimensions)
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
color-plot 〈P〉, all µ 48 / 57
lattice artifacts for µ > 7µc
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
color-plot 〈P〉, intermediate µ 49 / 57
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
µ-dependence of nq for different T 50 / 57
only states with vanishing total momentum contributesaturation for large µ, Nsat = 2× 16 = 32onset at µ = µc , steps of 2steps washed out with increasing T
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
color-plot nq , global picture 51 / 57
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
color-plot nq , intermediate µ 52 / 57
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
color-plot nq , small µ 53 / 57
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
color-plot ∂µnq , intermediate µ 54 / 57
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
color-plot ∂T nq , intermediate µ 55 / 57
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Conclusions and outlook 56 / 57
finite size/low temperature for high-density G2 in four dimensions?
evidence for first order nuclear matter transition
chiral symmetry restoration vs. confinement/deconfinement:
to this day not conclusive
deconfinement transition at lower temperatures / critical endpoint?
hybrid spectroscopy (difficult)
diquark condensation in 4d G2 and 2d two-flavour SU(2) at work
equations of state for µ ≤ 350 MeV
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature
Summary 57 / 57
G2 QCD is a useful laboratoryinterpolation G2-QCD→ QCD with Higgs-mechanism possiblefull phase diagram (in principle) accessible to simulationsfirst order(?) transition line (critical end point?)deformation vs. sign problem?testbed for model buildingtestbed for alternative approaches (expansions, renormalization group)?comparison with strong coupling / hopping parameter expansionsome of these questions can be answered in lower dimensions
Andreas Wipf (Jena) G2 Lattice Gauge Theory at Finite Density and Temperature