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simulation.
8µm LF.Monochromatic 8 µm luminosity ( L8µm) is known to correlate well with
the TIR luminosity [1, 6], especially for star-forming gala xies because the rest-frame
8µmﬂuxaredominatedbyprominentPAHfeaturessuchasat6.2,7 .7and8.6 µm.The
leftpanelofFig.1showsastrongevoltuionof8 µmLFs.Overplottedpreviousworkhad
torelyonSEDmodelstoestimate L8µmfromtheSpitzer S24µmintheMIRwavelengths
whereSEDmodelingisdifﬁcultduetothecomplicatedPAHemi ssions.Here,AKARI’s
mid-IR bands are advantageous in directly observing redshi fted restframe 8 µm ﬂux in
one of the AKARI’s ﬁlters, leading to more reliable measurem ent of 8µm LFs without
uncertaintyfromtheSED modeling.
12µm LF.12µm luminosity ( L12µm) represents mid-IR continuum, and known to
correlate closely with TIR luminosity [11]. The middle pane l of Fig.1 shows a strong
evoltuion of 12 µm LFs. Here the agreement with previous work is better becaus e (i)
12µm continuum is easier to be modeled, and (ii) the Spitzer also captures restframe
12µm inS24µmat z=1.
TIRLF.Lastly,weshowtheTIRLFsintherightpanelofFig.1.Weused Lagache,
Dole, & Puget [8]’s SED templates to ﬁt the photometry using t he AKARI bands
at>6µm (S7,S9W,S11,L15,L18WandL24). The TIR LFs show a strong evolution
comparedto localLFs. At 0 .25<z<1.3,L∗
TIRevolvesas ∝(1+z)4.1±0.4.FIGURE2. Evolutionof TIRluminositydensitybasedon TIRLFs (redcir cles),8µmLFs (stars), and
12µm LFs (ﬁlled triangles). The blue open squares and orange ﬁll ed squares are for LIRG and ULIRGs
only,alsobasedonour LTIRLFs.Overplotteddot-dashedlinesareestimatesfromtheli terature:LeFloc’h
et al. [9], Magnelli et al. [10] , Pérez-González et al. [11], Caputi et al. [2], and Babbedge et al. [1] are
in cyan, yellow, green, navy, and pink, respectively. The pu rple dash-dotted line shows UV estimate by
Schiminovichet al.[13].Thepinkdashedlineshowsthe tota lestimateofIR(TIRLF)andUV [13].
Cosmic star formation history .We ﬁt LFs in Fig.1 with a double-power law, then
integrate to estimate total infrared luminosity density at various z. The restframe 8
and 12µm LFs are converted to LTIRusing [11, 2] before integration. The resulting
evolution of the TIR density is shown in Fig.2. The right axis shows the star formation
densityassumingKennicutt[7].We obtain ΩIR(z)∝(1+z)4.4±1.0. Comparisonto ΩUV
[13] suggests that ΩTIRexplains 70% of Ωtotalatz=0.25, and that by z=1.3, 90% of
the cosmic SFD is explained by the infrared. This implies tha tΩTIRprovides good
approximationofthe Ωtotalatz>1.
In Fig.2, we also show the contributions to ΩTIRfrom LIRGs and ULIRGs. From
z=0.35 to z=1.4,ΩIRby LIRGs increases by a factor of ∼1.6, andΩIRby ULIRGs
increases byafactorof ∼10. Moredetailsarein Gotoet al. [3].
Spatially-Resolved Spectroscopy of an E+A (post-starburs t) System .We per-
formed a spatially-resolved medium resolution long-slit s pectroscopy of a nearby E+A
(post-starburst) galaxy system with FOCAS/Subaru [4]. Thi s E+A galaxy has an obvi-
ous companion galaxy 14kpc in front (Fig.3, left) with the ve locity difference of 61.8
km/s.
WefoundthatH δequivalentwidth(EW)oftheE+Agalaxyisgreaterthan7Å gal axy
wide (8.5 kpc) with no signiﬁcant spatial variation. We dete cted a rotational velocity in
the companion galaxy of >175km/s. The progenitor of the companion may have beenFIGURE 3. (left) The SDSS g,r,i-composite image of the J1613+5103. The long-slit position s are
overlayed.The E+A galaxy is to the right (west), with bluer c olour. The companion galaxy is to the left
(east). (right) H δEW is plotted against D4000. The diamonds and triangles are f or the E+A core/north
spectra, respectively. The squares and crosses are for the c ompanion galaxy’s core/north spectra. Gray
lines are population synthesis models with 5-100% delta bur st population added to the 10G-year-old
exponentially-decaying( τ=1Gyr)underlyingstellarpopulation.SalpeterIMFandmet allicityof Z=0.008
areassumed.Onthe models,burstagesof0.1,0.25,0.5and2 G yraremarkedwiththeﬁlled circles.
a rotationally-supported, but yet passive S0 galaxy. The ag e of the E+A galaxy after
quenching the star formation is estimated to be 100-500Myr, with its centre having
slightly younger stellar population. The companion galaxy is estimated to have older
stellarpopulationof >2 Gyrs ofagewithnosigniﬁcantspatialvariation(Fig.3, ri ght).
Theseﬁndingsareinconsistentwithasimplepicturewheret hedynamicalinteraction
createsinfallofthegasreservoirthatcausesthecentrals tarburst/post-starburst.Instead,
ourresultspresentanimportantexamplewherethegalaxy-g alaxyinteractioncantrigger
agalaxy-widepost-starburstphenomena.
REFERENCES
1. BabbedgeT.S.R., et al.,2006,MNRAS, 370,1159
2. CaputiK.I.,et al.,2007,ApJ,660,97
3. GotoT.,et al. 2010,A&AAKARI specialissue
4. GotoT.,YagiM.,YamauchiC., 2008,MNRAS, 391,700
5. HopkinsA.M.,ConnollyA. J.,HaarsmaD. B.,CramL. E.,200 1,AJ, 122,288
6. HuangJ.-S.,et al.,2007,ApJ, 664,840
7. KennicuttR. C.,Jr., 1998,ARA&A,36,189
8. LagacheG., DoleH.,PugetJ.-L.,2003,MNRAS, 338,555
9. LeFloc’hE.,etal., 2005,ApJ,632,169
10. MagnelliB., et al.2009,A&A,496,57
11. Pérez-GonzálezP. G.,etal., 2005,ApJ,630,82
12. RushB., MalkanM. A.,SpinoglioL.,1993,ApJS,89,1
13. SchiminovichD.,et al.,2005,ApJ, 619,L47
14. Wada T.,et al.,2008,PASJ, 60,517
arXiv:1001.0008v2 [hep-th] 6 Jan 2010Multi-Stream Inﬂation: Bifurcations and Recombinations i n the Multiverse
Yi Wang∗
Physics Department, McGill University, Montreal, H3A2T8, Canada
In this Letter, we brieﬂy review the multi-stream inﬂation s cenario, and discuss its implications in
the string theory landscape and the inﬂationary multiverse . In multi-stream inﬂation, the inﬂation
trajectory encounters bifurcations. If these bifurcation s are in the observable stage of inﬂation, then
interesting observational eﬀects can take place, such as do main fences, non-Gaussianities, features
and asymmetries in the CMB. On the other hand, if the bifurcat ion takes place in the eternal stage
of inﬂation, it provides an alternative creation mechanism of bubbles universes in eternal inﬂation,
as well as a mechanism to locally terminate eternal inﬂation , which reduces the measure of eternal
inﬂation.
I. INTRODUCTION
Inﬂation [1] has become the leading paradigm for the
very early universe. However, the detailed mechanism
for inﬂation still remains unknown. Inspired by the pic-
ture of string theory landscape [2], one could expect that
the inﬂationary potential has very complicated structure
[3]. Inﬂation in the string theory landscape has impor-
tantimplicationsinbothobservablestageofinﬂationand
eternal inﬂation.
The complicated inﬂationary potentials in the string
theory landscape open up a great number of interest-
ing observational eﬀects during observable inﬂation. Re-
searchesinvestigatingthecomplicatedstructureofthein-
ﬂationary potential include multi-stream inﬂation [4, 5],
quasi-single ﬁeld inﬂation [6], meandering inﬂation [7],
old curvaton [8], etc.

simulation.

8µm LF.Monochromatic 8 µm luminosity ( L8µm) is known to correlate well with

the TIR luminosity [1, 6], especially for star-forming gala xies because the rest-frame

8µmﬂuxaredominatedbyprominentPAHfeaturessuchasat6.2,7 .7and8.6 µm.The

leftpanelofFig.1showsastrongevoltuionof8 µmLFs.Overplottedpreviousworkhad

torelyonSEDmodelstoestimate L8µmfromtheSpitzer S24µmintheMIRwavelengths

whereSEDmodelingisdifﬁcultduetothecomplicatedPAHemi ssions.Here,AKARI’s

mid-IR bands are advantageous in directly observing redshi fted restframe 8 µm ﬂux in

one of the AKARI’s ﬁlters, leading to more reliable measurem ent of 8µm LFs without

uncertaintyfromtheSED modeling.

12µm LF.12µm luminosity ( L12µm) represents mid-IR continuum, and known to

correlate closely with TIR luminosity [11]. The middle pane l of Fig.1 shows a strong

evoltuion of 12 µm LFs. Here the agreement with previous work is better becaus e (i)

12µm continuum is easier to be modeled, and (ii) the Spitzer also captures restframe

12µm inS24µmat z=1.

TIRLF.Lastly,weshowtheTIRLFsintherightpanelofFig.1.Weused Lagache,

Dole, & Puget [8]’s SED templates to ﬁt the photometry using t he AKARI bands

at>6µm (S7,S9W,S11,L15,L18WandL24). The TIR LFs show a strong evolution

comparedto localLFs. At 0 .25<z<1.3,L∗

TIRevolvesas ∝(1+z)4.1±0.4.FIGURE2. Evolutionof TIRluminositydensitybasedon TIRLFs (redcir cles),8µmLFs (stars), and

12µm LFs (ﬁlled triangles). The blue open squares and orange ﬁll ed squares are for LIRG and ULIRGs

only,alsobasedonour LTIRLFs.Overplotteddot-dashedlinesareestimatesfromtheli terature:LeFloc’h

et al. [9], Magnelli et al. [10] , Pérez-González et al. [11], Caputi et al. [2], and Babbedge et al. [1] are

in cyan, yellow, green, navy, and pink, respectively. The pu rple dash-dotted line shows UV estimate by

Schiminovichet al.[13].Thepinkdashedlineshowsthe tota lestimateofIR(TIRLF)andUV [13].

Cosmic star formation history .We ﬁt LFs in Fig.1 with a double-power law, then

integrate to estimate total infrared luminosity density at various z. The restframe 8

and 12µm LFs are converted to LTIRusing [11, 2] before integration. The resulting

evolution of the TIR density is shown in Fig.2. The right axis shows the star formation

densityassumingKennicutt[7].We obtain ΩIR(z)∝(1+z)4.4±1.0. Comparisonto ΩUV

[13] suggests that ΩTIRexplains 70% of Ωtotalatz=0.25, and that by z=1.3, 90% of

the cosmic SFD is explained by the infrared. This implies tha tΩTIRprovides good

approximationofthe Ωtotalatz>1.

In Fig.2, we also show the contributions to ΩTIRfrom LIRGs and ULIRGs. From

z=0.35 to z=1.4,ΩIRby LIRGs increases by a factor of ∼1.6, andΩIRby ULIRGs

increases byafactorof ∼10. Moredetailsarein Gotoet al. [3].

Spatially-Resolved Spectroscopy of an E+A (post-starburs t) System .We per-

formed a spatially-resolved medium resolution long-slit s pectroscopy of a nearby E+A

(post-starburst) galaxy system with FOCAS/Subaru [4]. Thi s E+A galaxy has an obvi-

ous companion galaxy 14kpc in front (Fig.3, left) with the ve locity difference of 61.8

km/s.

WefoundthatH δequivalentwidth(EW)oftheE+Agalaxyisgreaterthan7Å gal axy

wide (8.5 kpc) with no signiﬁcant spatial variation. We dete cted a rotational velocity in

the companion galaxy of >175km/s. The progenitor of the companion may have beenFIGURE 3. (left) The SDSS g,r,i-composite image of the J1613+5103. The long-slit position s are

overlayed.The E+A galaxy is to the right (west), with bluer c olour. The companion galaxy is to the left

(east). (right) H δEW is plotted against D4000. The diamonds and triangles are f or the E+A core/north

spectra, respectively. The squares and crosses are for the c ompanion galaxy’s core/north spectra. Gray

lines are population synthesis models with 5-100% delta bur st population added to the 10G-year-old

exponentially-decaying( τ=1Gyr)underlyingstellarpopulation.SalpeterIMFandmet allicityof Z=0.008

areassumed.Onthe models,burstagesof0.1,0.25,0.5and2 G yraremarkedwiththeﬁlled circles.

a rotationally-supported, but yet passive S0 galaxy. The ag e of the E+A galaxy after

quenching the star formation is estimated to be 100-500Myr, with its centre having

slightly younger stellar population. The companion galaxy is estimated to have older

stellarpopulationof >2 Gyrs ofagewithnosigniﬁcantspatialvariation(Fig.3, ri ght).

Theseﬁndingsareinconsistentwithasimplepicturewheret hedynamicalinteraction

createsinfallofthegasreservoirthatcausesthecentrals tarburst/post-starburst.Instead,

ourresultspresentanimportantexamplewherethegalaxy-g alaxyinteractioncantrigger

agalaxy-widepost-starburstphenomena.

REFERENCES

1. BabbedgeT.S.R., et al.,2006,MNRAS, 370,1159

2. CaputiK.I.,et al.,2007,ApJ,660,97

3. GotoT.,et al. 2010,A&AAKARI specialissue

4. GotoT.,YagiM.,YamauchiC., 2008,MNRAS, 391,700

5. HopkinsA.M.,ConnollyA. J.,HaarsmaD. B.,CramL. E.,200 1,AJ, 122,288

6. HuangJ.-S.,et al.,2007,ApJ, 664,840

7. KennicuttR. C.,Jr., 1998,ARA&A,36,189

8. LagacheG., DoleH.,PugetJ.-L.,2003,MNRAS, 338,555

9. LeFloc’hE.,etal., 2005,ApJ,632,169

10. MagnelliB., et al.2009,A&A,496,57

11. Pérez-GonzálezP. G.,etal., 2005,ApJ,630,82

12. RushB., MalkanM. A.,SpinoglioL.,1993,ApJS,89,1

13. SchiminovichD.,et al.,2005,ApJ, 619,L47

14. Wada T.,et al.,2008,PASJ, 60,517

arXiv:1001.0008v2 [hep-th] 6 Jan 2010Multi-Stream Inﬂation: Bifurcations and Recombinations i n the Multiverse

Yi Wang∗

Physics Department, McGill University, Montreal, H3A2T8, Canada

In this Letter, we brieﬂy review the multi-stream inﬂation s cenario, and discuss its implications in

the string theory landscape and the inﬂationary multiverse . In multi-stream inﬂation, the inﬂation

trajectory encounters bifurcations. If these bifurcation s are in the observable stage of inﬂation, then

interesting observational eﬀects can take place, such as do main fences, non-Gaussianities, features

and asymmetries in the CMB. On the other hand, if the bifurcat ion takes place in the eternal stage

of inﬂation, it provides an alternative creation mechanism of bubbles universes in eternal inﬂation,

as well as a mechanism to locally terminate eternal inﬂation , which reduces the measure of eternal

inﬂation.

I. INTRODUCTION

Inﬂation [1] has become the leading paradigm for the

very early universe. However, the detailed mechanism

for inﬂation still remains unknown. Inspired by the pic-

ture of string theory landscape [2], one could expect that

the inﬂationary potential has very complicated structure

[3]. Inﬂation in the string theory landscape has impor-

tantimplicationsinbothobservablestageofinﬂationand

eternal inﬂation.

The complicated inﬂationary potentials in the string

theory landscape open up a great number of interest-

ing observational eﬀects during observable inﬂation. Re-

searchesinvestigatingthecomplicatedstructureofthein-

ﬂationary potential include multi-stream inﬂation [4, 5],

quasi-single ﬁeld inﬂation [6], meandering inﬂation [7],

old curvaton [8], etc.