IPMU International Conference

dark energy: lighting up the darkness!
program(final version)
June 2216:00-19:00

reception: cafeteria “Plaza Ikoi” in Kashiwa campus
June 23

09:30-09:40

welcome (H. Murayama)

09:40-10:20

opening review (M. Turner)cosmic microwave background

10:20-11:00

D. Spergel: What have we learned from the microwave background?

11:00-11:30

break

11:30-12:00

S. Ho: What can you do with CMB as a backlight?

12:00-12:30

J. Dunkley: Cosmology from the polarized CMB

12:30-14:10

lunch
theory, part I

14:10-14:50

L. Amendola: New observables for dark energy

14:50-15:20

M. Sami: Dark Energy: What could it be?

15:20-15:40

T. Chiba: The Equation of State of Slowly-Rolling Quintessence

15:40-16:10

break

16:10-16:30

K. Bamba: Phantom crossing in F(R) gravity

16:30-16:50

Y. Fujii: How successful can the scalar-tensor theory be in understanding
the accelerating universe?

16:50-17:10

M. Kasai: Out of darkness, towards inhomogeneity
June 24large scale structure

09:30-10:10

D. Eisenstein: Baryon Acoustic Oscillations: A Robust and Precise Route to
the Cosmological Distance Scale

10:10-10:40

U. Seljak: Dark energy from galaxy clustering: beyond BAO

10:40-11:10

break

11:10-11:40

O. Lahav: Cosmology from Photometric Redshift Surveys

11:40-12:00

A. Taruya: Non-linear evolution of matter power spectrum in modified theoryof gravity

12:00-12:20

T. Nishimichi: Accurate Modeling of Nonlinear Effects on Baryon Acoustic
Oscillations

12:20-14:00

lunch

14:00-14:20

S. Saito: How can we precisely determine both neutrino masses and darkenergy parameter through nonlinear galaxy power spectrum?
theory, part II

14:20-14:50

S. Mukohyama: Higgs phase of gravity and ghost condensation

14:50-15:10

S. Tsujikawa: Matter density perturbations in modified gravity models ofdark energy

15:10-15:30

L. Hui: Order Unity Equivalence Principle Violations in Modified Gravity

15:30-16:00

break

16:00-16:20

T. Kobayashi: Can higher curvature corrections cure the singularity problem
in f(R) gravity?

16:20-16:40

J.-A. Gu: An Approach to Testing Dark Energy Models by Observations

16:40-18:00

poster session

18:00-

public lecture: the Dark Side of the Universe (M. Turner)
June 25clusters

09:30-10:10

J. Mohr: Cluster Cosmology: Status and Prospects for the Coming Decade

10:10-10:40

A. Vikhlinin: Constraining Dark Energy with observations of structure growthusing X-ray galaxy cluster data

10:40-11:10

break

11:10-11:50

J. Carlstrom: Update on the South Pole Telescope SZ cluster survey

11:50-12:20

S. Staggs: Cosmology from the Atacama Cosmology Telescope

12:20-14:00

lunch

14:00-14:20

S. Majumdar: Self and External Mass Calibration in Cluster Studies of Dark
Energylensing, part I

14:20-15:00

G. Bernstein: The power of cosmic shear + galaxy redshift surveys

15:00-15:20

U. Seljak: Weak lensing and cluster abundance results from SDSS

15:20-15:50

break

15:50-16:20

M. Oguri: Cosmology with Strong Lensing: Current Status and Future
Directions

16:20-16:40

J. Jee: HST Weak-Lensing Study of >20 Galaxy Clusters Beyond RedshiftOnespecial talk on results from Fermi
16:40-17:10

T. Kamae: Fermi-LAT constraints on the dark-matter

18:30-

banquet: Crest Hotel
June 26
supernovae

09:30-10:10

G. Aldering: Advances in Cosmology with Type Ia Supernovae

10:10-10:40

N. Yasuda: Subaru contribution on supernova cosmology

10:40-11:10

break

11:10-11:40

D. Kasen: Physics of Type Ia Supernovae as Standardized Candles

11:40-12:00

K. Nomoto: Progenitors of Type Ia Supernovae

12:00-12:20

T. Moriya: Peculiar Type Ia Supernovae - Is It Really Type Ia?

12:20-14:00

lunch
lensing, part II

14:00-14:30

H. Aihara: Subaru Dark Energy Survey - Hyper Suprime-Cam Project

14:30-14:50

D. Clowe: Weak Lensing Tomography with Clusters of Galaxies

14:50-15:10

M. Takada: LoCuSS: Subaru Weak Lens Study of 30 Galaxy Clusters

15:10-15:30

break

15:30-15:50

S. Jouvel: Optimising cosmological Weak Lensing survey for future Dark
Energy space mission

15:50-16:10

A. Amara: Weak Lensing From Space: Prospects and Challenges for Euclid

16:10-16:30

conference summary (N. Sugiyama)

If you spot any error please contact the LOC (darkenergy09@ipmu.jp) for corrections. Thank you!

list of posters(final version)#

first author

title

1

Leopoldo Infante

The ISW@VST survey

2

Masatoshi Shoji

Third-order Perturbation Theory with Non-linear Pressure

3

Atsushi Nishizawa

Impact of photometric redsfhit error on the dark energy measurement4

Keiichi Maeda

Asymmetry in Supernovae Explosions

5

Issha Kayo

A model independent method to measure pairwise velocity dispersion of galaxies

6

Donghui Jeong

Effect of non-linearities and non-Gaussianities on measuring cosmological distances

7

M. Nakashima

New Constraint on the varying fine structure constant8

Yasuomi Kamiya

Intrinsic Color Dispersion of Type Ia Supernovae

9

Masanori Sato

Simulations of Wide-Field Weak Lensing Surveys: Basic Statistics and NonGaussian Effects

10

Satej Khedekar

Constraining cosmology using clusters as an ensemble of cosmic rulers

11

Dai G. Yamazaki

Dark energy, Finite-mass Neutrino, and Primordial Magnetic Field

12

Tomonori Furukawa

Ghost condensation in cosmology

13

Kiyotomo Ichiki

Constraining the nature of dark energy from recent observations and its relation to
inflation parameters

14

Maresuke Shiraishi

Constraints on the cosmological constant from WMAP5 and BBN if neutrinos havefinite masses and chemical potentials

15

Ilya Gurwich

Natural Neutrino Dark Energy

16

Kensuke Homma

Probing light scalar/pseudoscalar fields by extremely strong laser-laser diffraction

17

Shoichi Ichinose

Renormalization Flow of Cosmological Constant18

Hyeong-Chan Kim

Dark energy from Cosmic Hawking radiation

19

H. Motohashi

Evolution of density fluctuation in f(R) gravity

20

Fuminobu Takahashi

Strong CP problem and cosmological constant

21

Tomo Takahashi

Testing dark energy models: possible complications and some issues of dark energy
perturbations

22

Yuko Urakawa

Can we rule out unified dark matter models?

23

M. Sohaib Alam

Signatures in the CMB of Pre-Inflation Anisotropy

24

Grant Mathews

Constraints on Some Alternative Unifying Views of Dark Energy and Dark Matter

Logistics
Opening reception
Opening reception will be held during 16:00 - 19:00 on June 22 (Mon) at the university
cafeteria "Plaza Ikoi" in the Kashiwa Campus. Some drink and light food will be provided.
The campus map is available at
http://www.u-tokyo.ac.jp/campusmap/cam03_04_11_e.html.
The red-color building in the map above is the cafeteria; the left-lower, gray-color buildingis the conference venue, Kashiwa Library Media Hall.
No shuttle bus will be provided between hotels in Kashiwa and the campus for the
reception. Please come to the cafeteria by yourself. You can find the ways to get to thecampus from http://www.ipmu.jp/visitors/access-ipmu.

Shuttle bus
During June 23 - 26, two shuttle buses will be provided every morning and every evening.
The schedule is the following:morning:~8:15am (Mitsui Garden Hotel) - 8:30am (Crest Hotel) - 9:00 (campus)
evening:
Tue: 17:30 (campus) - 18:00 (Crest Hotel) - 18:15 (Mitsui Garden Hotel)
Wed: 17:30 (campus) - 18:00 (Crest Hotel) - 18:15 (Mitsui Garden Hotel)
Thu: 17:45 (campus) - 18:15 (Crest Hotel) - 18:30 (Mitsui Garden Hotel)
Fri: 16:45 (campus) - 17:15 (Crest Hotel) - 17:30 (Mitsui Garden Hotel)
Every bus will stop at the Mitsui Garden Hotel and the Crest Hotel, both of which are close
to the Japan Rail (JR) Kashiwa station.
After the public lecture on Wednesday, additional buses will leave from the campus at
20:00, and go to Kashiwa-no-ha Campus Station and JR Kashiwa station.

Food
Light breakfast (bread, coffee, and tea) will be provided before the morning session. No
lunch will be provided, but we will have lunch at the university cafeteria, the same place as
the opening reception.

Public lecture
Prof. Michael Turner kindly agreed to give a public lecture “The dark side of the Universe”
to the general public at the Kashiwa Library Media Hall, from 18:00 to 19:30 on June 24.
The talk is in English, but the presentation will be translated into Japanese. You are very
welcome to join the public lecture. The shuttle bus after the public lecture will be provided
as mentioned above.

Conference banquet
The banquet will be held at the Crest Hotel from 18:30 on June 25. An on-site registration
for banquet is still available, so just stop by the registration desk if you want to join.

Poster presentation
The poster presentation will be held at the Kashiwa Library Media Hall. The size of poster
panel is width x height = 90 x 210 cm, such that an A0-sized poster is well fitted. Eachposter is assigned an ID number as indicated in the poster list. Please put your poster onto
the panel with the same ID number.

Contributed Talks: abstract
Weak Lensing From Space: Prospects and Challenges for Euclid
Adam AmaraETH Zurich
Gravitational lensing allows us to measure dark matter in the low redshift Universe. From
this we can construct a history of how structures have grown and how the Universe has
evolved. Given the great promise of this technique, considerable resources are being
channelled into developing surveys to measure lensing over the whole sky. I will give an
update on the potential that missions such as Euclid (which is part of the ESA Cosmic
Vision Program) have for measuring dark matter, dark energy and initial conditions in the
Universe. Euclid will also provide a strong test of Einstein gravity. I will briefly discuss thestrength and possible pitfalls of a weak lensing approach. The success of lensing surveys
over the coming decade will depend on our ability to control systematics, as wellmaintaining a sensible cost cap on missions. Euclidʼs strategy for achieving these goals is
to take full advantage of a ground-space synergy, in which we us ground-base data where
possible and do in space only what could only be done in space, namely high resolution
imaging and deep Near-IR photometry and spectroscopy.

Phantom crossing in F(R) gravity
Kazuharu Bamba
National Tsing Hua University
A scenario to explain the current accelerated expansion of the universe is to study amodified gravitational theory, such as F(R) gravity, in which the action is described by anarbitrary function F(R) of the scalar curvature R. On the other hand, various observational
data imply that the ratio of the effective pressure to the effective energy density of theuniverse, i.e., the effective equation of state (EoS), may evolve from larger than -1 (nonphantom phase) to less than -1 (phantom phase). Namely, it crosses (or crossed) -1 (thephantom divide) at the present time (or in near past). In this presentation, we reconstruct
an explicit model of F(R) gravity with realizing a crossing of the phantom divide.
Reference: Phys. Rev. D 79, 083014 (2009) [arXiv:0810.4296 [hep-th]]

The Equation of State of Slowly-Rolling Quintessence
Takeshi Chiba
Nihon University

I derive slow-roll conditions for quintessence. I solve the equation of motion in the limit
where the equation of state w is close to -1 to derive the equation of state as a function of
the scale factor. I find that the equation of state involves only two parameters and its
evolution is not fit by a linear function of the scale factor.

Weak Lensing Tomography with Clusters of Galaxies
Douglas Clowe
Ohio University
I will discuss uses of weak lensing caused by massive clusters of galaxies in constraining
dark energy, and how, in particular, one may use this technique to measure the effects ofdark energy from geometry along (no dependence on the rate of structure growth). I will
discuss an initial attempt to do this with existing HST images of galaxy clusters, and how
such studies can be performed as supplemental measurements of dark energy from large
area imaging surveys.

How successful can the scalar-tensor theory be in understanding the accelerating
universe?
Yasunori Fujii
Waseda University
The accelerating universe is best described in terms of a small cosmological constant,which, through todayʼs version of the cosmological constant, or the twin questions; finetuning and coincidence problems, likely requires the presence of a scalar field. The
scalar-tensor theory invented by P. Jordan in 1955, can be developed successfully beyond
expectation. Through a better understanding of conformal transformations and frames
from a physical point of view we reach a consistent way to interpret the Jordan andEinstein frames for the theoretical and physical frames, respectively. In particular, we
implement the scenario of a decaying cosmological constant; $ Lambda_{\\rm eff}\\simt^{-2}$, numerically realized by $10^{-120}\\sim (10^{60})^{-2}$ with the present age of theuniverse $1.37 \\times 10^{10}{\\rm y}\\approx 10^{60}$ in units of the Planck time,showing that todayʼs $\\Lambda$ is extremely small not because of fine-tuning parameters
but only because we are old. This success is regarded as one of the most remarkableachievements of the scalar-tensor theory, though we must go through rather complicatedmodifications beyond the simplest version, including the technical details from the scaling
to tracking behaviors, to arrive at realistic fits to the observed acceleration.

An Approach to Testing Dark Energy Models by Observations
Je-An Gu
National Taiwan University
An approach to the consistency test of dark energy models with observations will bepresented. To test a dark energy model, we suggest introducing a characteristic Q(z) thatin general varies with the redshift z but in that model plays the role of a constant distinct
parameter. Then, by reconstructing dQ(z)/dz from observational data and comparing it withzero we can assess the consistency between data and the model under consideration. For
a model that passes the test, we can further constrain the distinct parameter of that modelby reconstructing Q(z) from data. For reconstructing Q(z) and dQ(z)/dz from data, aparametrization of the relevant physical quantity is required. For demonstration, we invoke
a widely used parametrization of the dark energy equation of state, w(z) = w_0 + w_a (1a), for data analysis. This method of the consistency test is efficient because for all models
we invoke the constraint of only a single parameter space that by choice can be easily
accessed. The general principle of our approach is not limited to dark energy. It may also
be applied to the testing of various cosmological models and even the models in otherfields beyond the scope of cosmology.

Order Unity Equivalence Principle Violations in Modified Gravity
Lam Hui
Columbia University
Theories that modify general relativity in an attempt to explain cosmic acceleration
inevitably introduce extra degrees of freedom, notably a scalar. This encompasses all
known theories, including f(R), DGP, degravitating models and generalizations thereof.
Such a scalar must be screened on small scales to be consistent with solar system andterrestrial experiments. In this talk, I will show that depending on the screening
mechanism, there can be order one violations of the equivalence principle i.e. different
objects will fall at different rates. Small galaxies in cosmic voids provide the mostpromising places to look for such effects.

HST Weak-Lensing Study of >20 Galaxy Clusters Beyond Redshift One
James Jee
University of California, Davis
We study more than 20 galaxy clusters at z>1 through HST weak gravitational lensing.
Despite the challenges set by the substantially reduced number density of backgroundgalaxies and the intrinsically low masses of these high-z clusters, we are able to measurea significant (>10 sigma) lensing signal from most of these high-redshift clusters. Together
with the two-dimensional mass maps, we present our preliminary mass-temperature
relation at z>1, and discuss the mass function and its cosmological implications.

Optimising cosmological Weak Lensing survey for future Dark Energy space
missionStephanie Jouvel
Laboratoire d’Astrophysique de Marseille
Cosmological weak lensing has emerged as one of the most effective dark energy probe(Dark Energy Task Force report) as it is both sensitive to the Universe geometry and to thegrowth of structures. In order to construct the most efficient cosmological weak lensing
survey, one first needs to have a good understanding of galaxy properties (redshift,luminosity, spectro-photometry, size, morphology and types), as they are the tracers used
to measure the weak lensing signal. Extrapolating from current observations of the deep
Universe, I have explored different ways to produce representative mock catalog of thegalaxy distribution as they will be observed by future space-based mission. This work was
more specifically conducted in the context of the SNAP/JDEM mission. These realistic
mock catalogs are unique tools to explore the impact of the surveys parameters (mirrors
transmission, number of filters, and filter shapes, detectors efficiency, pixel size, survey
strategy). Using those catalogs, I have revisited the photometric parameters of the survey
in order to improve the redshift bias, redshift dispersion and minimize the number ofcatastrophic redshift. In this presentation, I will talk about these mock catalogs and survey
designs of future dark energy mission derived from the photometric redshift accuracy forweak-lensing measurements.

Out of darkness, towards inhomogeneity
Masumi Kasai
Hirosaki University
I briefly review the backreaction of nonlinear inhomogeneities to the cosmic expansion,
with some historical remarks. Then I propose an inhomogeneous viewpoint that theapparent acceleration of the cosmic expansion is a consequence of large-scale
inhomogeneities in the universe.

Can higher curvature corrections cure the singularity problem in f(R) gravity?
Tsutomu Kobayashi
Waseda University
Although $f(R)$ modified gravity models can be made to satisfy solar system andcosmological constraints, it has been shown that they have the serious drawback of thenonexistence of stars with strong gravitational fields. In this paper, we discuss whether or
not higher curvature corrections can remedy the nonexistence consistently. The following
problems are shown to arise as the costs one must pay for the $f(R)$ models that allow forneutrons stars: (i) the leading correction must be fine-tuned to have the typical energy
scale $\mu \lesssim 10^{-19}$ GeV, which essentially comes from the free fall time of a
relativistic star; (ii) the leading correction must be further fine-tuned so that it is not givenby the quadratic curvature term. The second problem is caused because there appears anintermediate curvature scale and laboratory experiments of gravity will be under the
influence of higher curvature corrections. Our analysis thus implies that it is a challenge toconstruct viable $f(R)$ models without very careful and unnatural fine-tuning.

Self and External Mass Calibration in Cluster Studies of Dark Energy
Subha Majumdar
Tata Institute of Fundamental Research
Upcoming surveys of clusters of galaxies, with large yields, have the potential to probe
cosmological parameters (like properties of Dark Energy ) with precision. The major
systematic in such efforts is our incomplete understanding of the connection between theobservables and the underlying cluster mass which is the one parameter link to numericalsimulations. One needs do follow-up mass measurements to high redshifts to understandand quantify such a connection. On the other hand, it has been shown that the data is richenough to do cosmology and self-calibrate this connection at the same time. In this brieftalk, I discuss some issues related to the two approaches.

Peculiar Type Ia Supernovae - Is It Really Type Ia?
Takashi Moriya
The University of Tokyo
On November 7, 2008, supernova (SN) 2008ha was first detected in an irregular galaxy
UGC 12682 and found to be one of the faintest supernovae ever discovered. Since its
spectra are similar to those of a peculiar Type Ia SN 2002cx, SN 2008ha was firstclassified as a member of the peculiar subclass of SNe Ia. However, because of the lowvelocity spectra and rapid evolution of the light curve, some studies suggest that SN
2008ha is originated from a core collapse explosion, not a thermonuclear explosion. We
perform hydrodynamical simulations of core-collapse SN explosions with low explosion
energies and show that a very faint supernova can be led from a core collapse explosion.
In such weak explosions, the most part of the stellar envelope falls back to the central
remnant and only the outer most layers are ejected. We compare the observations of SN
2008ha with our results and see whether it is possible to reproduce its light curve andspectra. Furthermore, we present characteristics of the extremely faint class of corecollapse SNe.

Accurate Modeling of Nonlinear Effects on Baryon Acoustic Oscillations
Takahiro Nishimichi
The University of Tokyo
The baryon acoustic oscillations (hereafter BAOs) are important tools to access to thenature of dark energy. On-going and up-coming wide and deep galaxy redshift surveys aresupposed to measure the characteristic scale of BAOs very accurately, and we need toconstruct an accurate theoretical template to confront with the observations. We will report
the current status of our theoretical template for the galaxy power spectrum (or the twopoint correlation function) constructed by theoretical models and N-body simulations. We
model the nonlinear growth of matter clustering with 1% accuracy at the scale of BAOs ink-space. We also investigate the accuracy of matter clustering in redshift space, and foundthat the achieved accuracy is well within the statistical error expected from the WFMOS
survey. We will also address the current investigation on the halo clustering in our N-bodysimulations.

Progenitors of Type Ia Supernovae
Ken Nomoto
IPMU
We present quantitative binary evolution models for both single degenerate and double
degenerate cases. By clarifying the possible range of binary parameters to realize Type Ia
Supernovae (SNe Ia), we discuss why the single degenerate model for SNe Ia is moreplausible. We then present a theoretical delay time distribution of SNe Ia to compare withobservations.

How can we precisely determine both neutrino masses and dark energy
parameter through nonlinear galaxy power spectrum?
Shun Saito
The University of Tokyo
Baryon Acoustic Oscillations (BAOs) imprinted in galaxy power spectrum is powerful tool
to determine the distance scale of the universe and therefore the equation of state of darkenergy. The key issues to achieve the high accuracy are nonlinearities such as
gravitational evolution, galaxy biasing, and redshift distortions in galaxy distribution.
Moreover, in recent studies on these issues, the effect of massive neutrinos are basicallyneglected just for simplicity. However considering the percent level measurement of power
spectrum, the effect of massive neutrinos cannot be neglected. This is because, at smallerscale than neutrino free-streaming where nonlinearity is important, neutrinos suppress theamplitude of power spectrum at more than one percent level. In this work, we show the
impact of massive neutrinos on determination of dark energy parameter including
nonlinear effects on galaxy power spectrum.

LoCuSS: Subaru Weak Lens Study of 30 Galaxy Clusters
Masahiro Takada
IPMU
We use Subaru data to conduct a detailed weak-lensing study of the dark matter
distribution in a sample of 30 X-ray luminous galaxy clusters at 0.15<z<0.3. We in detail
explore the best-available accuracy of estimating cluster masses from weak lensing
information, for each cluster basis and for stacked cluster signals and using several
methods (the model profile fitting and the model-independent aperture mass estimate).
Some highlights of our findings are (1) cluster mass enclosed by the spherical over-density

500 can be constrained at 10-20% accuracy for individual clusters and (2) the mass-haloconcentration scaling relation is found at a 2-sigma level.

Non-linear evolution of matter power spectrum in modified theory of gravity
Atsushi Taruya
The University of Tokyo
We present a formalism to calculate the non-linear matter power spectrum in modified
gravity models that explain the late-time acceleration of the Universe without dark energy.
Any successful modified gravity models should contain a mechanism to recover General
Relativity (GR) on small scales in order to avoid the stringent constrains on deviations from
GR at solar system scales. Based on our formalism, the quasi non-linear power spectrum
in the Dvali-Gabadadze-Porratti (DGP) braneworld models and $f(R)$ gravity models arederived by taking into account the mechanism to recover GR properly. We also extrapolate
our predictions to fully non-linear scales using the Parametrized Post Friedmann (PPF)
framework.We find that the mechanism to recover GR suppresses the difference between
the modified gravity models and dark energy models with the same expansion history, but
the difference remains large at weakly non-linear regime in these models.

Matter density perturbations in modified gravity models of dark energy
Shinji Tsujikawa
Tokyo University of Science
We derive the equation of matter density perturbations on sub-horizon scales for a general
Lagrangian density f(R, phi, X) that is a function of a Ricci scalar R, a scalar field phi anda kinetic term X. This is useful to constrain modified gravity dark energy models fromobservations of large-scale structure and weak lensing. We obtain the solutions for thematter perturbation as well as the gravitational potential for some analytically solvablemodels. We also estimate the growth factor of matter perturbations in f(R) gravity andscalar-tensor models, which shows notable differences from the LCDM model.

Poster Presentations: abstract
Signatures in the CMB of Pre-Inflation Anisotropy
M. Sohaib AlamThe University of Texas, Austin
We explore the statistics of the two-point correlation functions, assuming a backgroundthat at the beginning of inflation was anisotropic but homogeneous and described by a
Bianchi type I metric. It has been known for a while that the inflaton field dynamicallydrives this background to a regular FRW metric. Under the assumption that the number of
e-foldings is sufficiently small so that not all of the primordial anisotropy is wiped out, we
explore the statistics of the two-point correlation function assuming Gaussianity. The
results are then to be compared against CMB data to yield constraints on the extent of
anisotropy that could have existed before inflation.

Ghost condensation in cosmology
Tomonori Furukawa
Nagoya University
As a model of explaining an accelerating universe today, the ghost condensate isconsidered. This is the fluid and modification of gravity. However, it is little known how thefluid evolve as universe expands. So we calculate the evolution of the simplest of ghost
condensation model in FRW background and constrain parameter.

Natural Neutrino Dark Energy
Ilya Gurwich
Ben-Gurion University
The observed value of the cosmological constant seems to be in disagreement with thenatural scale of gravity and most of the emerging scales in QFT. We are therefore urged toseek a different source for dark energy with a natural scale similar to that of thecosmological constant. The fact that the neutrino mass seems fit the scale of the vacuum
energy (\Lambda/G), seems to offer an intriguing window of opportunity. I will review theapproaches to neutrino dark energy and present a new one that requires no additional
physics. Vacuum-matter interaction leads to a "Casimir-like" effect, that generates aconstant energy density proportional to the mass^4 of the field. This energy becomes
exponentially suppressed when the effective temperature drops below the mass of the
field. This will result in an effective phase transition and serves as an explanation as towhy we do not observe the contribution of the more massive fields. This model suggests

that the value of the cosmological constant was higher in the early universe and will belower in the future, thus also resolving the cosmic coincidence puzzle. I will also discuss
the quantum ambiguity of this model. Finally, I will present the possible future
observational verifications of this model, including the predicted DE equation of state,larger cosmological constant in the past and traces of the phase transitions.

Probing light scalar/pseudoscalar fields by extremely strong laser-laser
diffraction
Kensuke Homma
Hiroshima University
If the dark energy is attributed to the quantum nature of the vacuum, it must be probed
even at laboratory experiments. A possibility to explain the observed energy density of(2.39meV)^4 is the assuption of omnipresent light stable fileds with the mass of ~1meV
and the small coupling to matters beyond the age of the present universe. By aiming at theworld's first observation of real photon-photon interactions in QED in the lower frequency
range, we can generally measure the macroscopic birefringence of the vacuum under
extremely strong laser fileds. If the birefringence significantly deviates from what is
expected in QED, it can be an indication of the coupling of the light fields to two photons(an effect of finite long range force). We would like to present a concrete experimental
setup to search for the effect of such light fileds.

Constraining the nature of dark energy from recent observations and its relation
to inflation parameters
Kiyotomo Ichiki
Nagoya University
We investigate how the nature of dark energy affects a test of inflation. For this purpose,the constraints on the primordial fluctuation, in particular the scalar spectral index, its
running and the amplitude of tensor mode are studied in models with a generalized darkenergy. Usually a cosmological constant is assumed when one investigates observational
constraints on such quantities. However, we do not know the nature of dark energy yet, it
may be premature to assume a cosmological constant as dark energy. In this poster, we
assume a generalized dark energy to obtain the constraints on the primordial fluctuationand then discuss the implications on the early universe. By using the current cosmological
data from cosmic microwave background, large scale structure and so on, we show how
the allowed region can be changed depending on what type of dark energy is assumed.
The limits on the parameters of generalized dark energy from recent and near future
observations are also presented.

Renormalization Flow of Cosmological Constant
Shoichi Ichinose
University of Shizuoka

We approach the problem of the dark energy and the cosmological constant from the extra
dimension model. We introduce a new type regularization, called "sphere lattice
regularization" in order to control the UV-divergences. Using the 5D Electromagnetism on
the AdS5 background curved space, we succeed in obtaining the finite Casimir energy andits renormalization property. The smallness of the cosmological constant is naturally
understood as the flow. Related references: ArXiv: 0903.4971, 0812.1263

The ISW@VST survey
Leopoldo InfantePonfiticia Universidad Catolica de Chile
We plan to carry out a southern 5000 deg^2 deep survey of galaxies in the $r$ band to
detect the Integrated Sachs-Wolfe Effect with a signal to noise ratio 40\% higher than any
other survey so far (e.g. SDSS DR4) . The aim is to determine the equation of state of theuniverse by cross-correlating this galaxy map with high resolution CMB anisotropy maps
from existing WMAP and future Planck observations. In this contribution we show that we
can reach a near-maximum S/N value of the ISW effect using a single broad-band (r-band)
spatially-contiguous galaxy catalog with a mean redshift = 1.2 at a particular scale of thesky (0.5 deg^2). Furthermore, galaxy binning it is not required and therefore redshift
information is not needed for all galaxies to compute the ISW effect. To cover the desired
field, 64 nights in 4 years (r_AB<~23.8, 16 dark-grey 1.0 arcsec seeing nights per year)
would be required with a survey telescope like ESO-VST. The ISW results from this survey
will surpass the results from SDSS, because of its depth, and be comparable to the resultsof the Dark Energy Survey, but 3 years earlier.

Effect of non-linearities and non-Gaussianities on measuring cosmologicaldistances
Donghui Jeong
The University of Texas, Austin
We analyze the effect of non-linearities and primordial non-Gaussianities on measuring theangular diameter distance and Hubble expansion rate at high redshift from the galaxy
power spectrum.

Intrinsic Color Dispersion of Type Ia Supernovae
Yasuomi Kamiya
The University of TokyoA Type Ia Supernova is thought to explode when a mass of a carbon-oxygen white dwarf
in a close binary system becomes very close to a Chandrasekhar mass. Thus, Type Ia
Supernovae are expected to have homogeneous properties and used as (correctable)
standard candles in cosmology. However, recent studies show that Type Ia Supernovae dohave intrinsic dispersion. For instance, there is dispersion in (U-B)--(B-V) diagram, where
the data are used at the time of the maximum magnitude in the B band. This observed
dispersion is not explainable by the extinction in the Milky Way and in the host galaxies ofType Ia Supernovae. In order to study this intrinsic dispersion of Type Ia Supernovae, we
performed multi-frequency time-dependent radiation transfer simulations. We show thatthe dispersion can originate from varieties of the 56Ni mass and of the mixing degree inthe ejecta. The less synthesized 56Ni is, and the more extensive mixing is, the redder U-B
and B-V become. This can explain the dispersion in the color-color diagram.

A Model independent method to measure pairwise velocity dispersion of galaxies
Issha Kayo
IPMU
We have developed a method to measure large-scale velocity dispersion of galaxies. Thismethod is based on Peebles(1980) and improved so as to handle the feature of the twopoint correlation function at large scale more properly. It does not require strong
assumptions on the shape of the probability distribution function of the pairwise velocity
contrary to ordinary methods where Gaussian or exponetial forms are often adopted. We
checked and tuned the method using N-body simulations and applied it to the SDSS
galaxy data. Using the method, we evaluated the luminosity dependence of the velocity
dispersion of the SDSS galaxies and confirmed the non-monotonic feature found by Jing &Boerner (2004).

Constraining cosmology using clusters as an ensemble of cosmic rulers
Satej Khedekar
Tata Institute of Fundamental Research
Abundance and distribution of clusters of galaxies depend on the expansion history of the
Universe as well as the growth of cosmic structures. On the other hand, a measurement of
the angular diameter distance as a function of redshift depends on the expansion history.
These can be used as complimentary probes of cosmology. These distances may be
estimated in two ways- 1) By joint measurement of clusters in both XRays and SZ fromsurveys with overlapping sky coverage, and; 2) By measuring the isophotal size of clusters
in a survey. We probe the above mentioned complementarity using clusters and show thatby combining cluster number count observations with distance measurements, one canbreak the cosmological parameter degeneracies. Especially, there is significant
improvement on dark energy constraints. Our estimates promises another promising
application of upcoming cluster data.

Dark energy from Cosmic Hawking radiation
Hyeong-Chan Kim
Chungju National University
We suggest that dark energy is the energy of Hawking radiation from a cosmic horizon due
to quantum vacuum fluctuations. (JCAP0708:005,arXiv:0803.1987). It is well known thatfor the De Sitter universe the Hawking radiation has the equation of state -1 but O(H^4)
energy density after renormalization, where H is the Hubble parameter. However, using thequantum field theory on curved space-time we show that if there is a Planck scale UVcutoff this energy density is O(H^2 M_P^2) which is comparable to the observed darkenergy density. The Hawking radiation also has an appropriate equation of state
consistent with the observed value.

Asymmetry in Supernovae Explosions
Keiichi Maeda
IPMU
We present observational support and test for the explosion asymmetry in supernova (SN)
explosions, both for core-collapse SNe from massive stars and Type Ia SNe used as
standard distance indicators. Identifying the SN explosion asymmetry is a key tounderstand still-unresolved explosion mechanisms. This may also be important to develop
better luminosity indicators for SNe Ia than currently used. We have been proposing to use
late-time spectra in optical and NIR, taken about an year after the explosion, in order totackle this issue. Theoretical expectations based on our numerical investigations of the
explosive nucleosynthesis and radiation transfer are compared with the observationaldata, partly obtained by ourselves with the Subaru Telescope.

Constraints on Some Alternative Unifying Views of Dark Energy and Dark Matter
Grant Mathews
University of Notre Dame
The simple fact that the present closure contributions from dark matter and dark energy
are nearly equal begs the question as to whether they could be different aspects of thesame physical phenomenon. Here, we review constraints several postulates as to how
this coincidence might have been achieved. AMong the topics we have analyzed are:1)
The possibility that the dark matter decays producing a bulk viscosity in the cosmic fluid; 2)
the cosmic acceleration is produced by the inflow of dark matter from a bulk dimension inbrane-world cosmology; and 3) The possibility that relativistic corrections to the Friedmannequation from the presence of local inhomogeneities produce acceleration terms.
Constraints and observational tests of each of these cosmologies are proposed. We findthat all of these paradigms can either be ruled out or require such fine tuning that they are
unlikely as a source for dark energy. Nevertheless, future observations may find some of
the unique signatures which we identify for such alternative unified models.

Evolution of density fluctuation in f(R) gravity
Hayato Motohashi
The University of Tokyo
There are many models to explain cosmic acceleration or dark energy. Though LCDM
model is a simplest solution, the model has some difficulties. One of the alternative

approaches is f(R) gravity. We consider the evolution of density perturbation in f(R) modeland compare it with observation.

New Constraint on the varying fine structure constant
Masahiro Nakashima
The University of Tokyo
We present new constraints on the time variation of the fine structure constant at
recombination epoch relative to its present value taking into account simultaneous
variation of other physical constants, the electron mass and the proton mass. Under someunification theory motivated relations between the variation of these constants, we obtaintighter constraints than those in the previous work in which the variation of the proton
mass was not included. Furthermore, we investigate the degeneracy of other parameterswith varying constants, in particular, the degeneracy between the fine structure constantand the dark energy equation of state.

Impact of photometric redsfhit error on the dark energy measurement
Atsushi Nishizawa
The University of Tokyo
The weak lensing is expected to be a powerful tool for constraining dark energy
parameters. However it includes many systematic uncertainties. One of the most importantsystematic error is caused by photometric redshift of background galaxies, i.e. lensed
galaxies. We develop a new method to improve the photometric redshift uncertainty by
discarding so called outliers, whose photometric redshifts are catastrophicallymisestimated. Generally speaking, they have a broad, sometimes bimodal distribution inthier chi square distribution. We quantify the broadness of distribution function, andsuccess to identify the outliers. Assuming a upcoming weak lensing survey, for example,
Hyper Suprime-Cam on Subaru, at most 70% galaxies should be discarded in order toachieve the systematic error on equation of state to be comparable with statistical one.

Simulations of Wide-Field Weak Lensing Surveys: Basic Statistics and NonGaussian Effects
Masanori Sato
Nagoya University
We run 400 cosmological N-body simulations to study the lensing convergence power
spectrum and its covariance for a standard CDM cosmology. We use the outputs toperform a total of 1000 independent ray-tracing simulations. We compare the simulation
results with analytic model predictions. The semi-analytic model based on Smith et al.
(2003) fitting formula underestimates the convergence power by ~30% at arc-minuteangular scales. For the convergence power spectrum covariance, the so-called halo model
reproduces the simulation results remarkably well over a wide range of angular scales andsource redshifts. The signal-to-noise ratio for the convergence power spectrum isdegraded by the non-Gaussian covariances by up to a factor 5 for a weak lensing survey
to z~1. The probability distribution of the convergence power spectrum estimators, among
the realizations, is well approximated by a ^2-distribution with broadened variance givenby the non-Gaussian covariance, but has a larger positive tail. The skewness and kurtosis
have non-negligible values especially for a shallow survey. We argue that a priorknowledge on the full distribution may be needed to obtain an unbiased estimate on theensemble averaged band power at each angular scale from a finite volume survey.

Constraints on the cosmological constant from WMAP5 and BBN if neutrinos havefinite masses and chemical potentials
Maresuke Shiraishi
Nagoya University
In this conference, I present constraints on the cosmological constant and neutrino
properties from WMAP5 data and light element abundances by using a Markov chain
Monte Carlo (MCMC) approach. In order to take consistently into account the effects ofneutrino chemical potentials, I ran the Big Bang Nucleosynthesis code for each value ofneutrino chemical potentials and the other cosmological parameters to estimate theHelium abundance, which is then used to calculate CMB anisotropy spectra instead oftreating it as a free parameter. I found that the constraint on the cosmological constantslightly changes if the lepton asymmetry is allowed.

Third-order Perturbation Theory with Non-linear Pressure
Masatoshi Shoji
The University of Texas, Austin
We calculate the non-linear matter power spectrum using the 3rd-order perturbation theory
without ignoring the pressure gradient term. We consider a semi-realistic system
consisting of two matter components with and without pressure, and both are expanded
into the 3rd order in perturbations in a self-consistent manner, for the first time. While thepressured component may be identified with baryons or neutrinos, in this paper we mainly
explore the physics of the non-linear pressure effect using a toy model in which the Jeans
length does not depend on time, i.e., the sound speed decreases as a-1/2, where a is thescale factor. The linear analysis shows that the power spectrum below the so-called
filtering scale is suppressed relative to the power spectrum of the cold dark matter. Our
non-linear calculation shows that the actual filtering scale for a given sound speed issmaller than the linear filtering scale by a factor depending on the redshift and the Jeans
length. A ~40% change is common, and our results suggest that, when applied to baryons,the temperature of the Inter-galactic Medium inferred from the filtering scale observed in
the flux power spectrum of Lyman-alpha forests would be underestimated by a factor of
two, if one used the linear filtering scale to interpret the data. The filtering mass, which is
proportional to the filtering scale cubed, can also be significantly smaller than the linear
theory prediction especially at low redshift, where the actual filtering mass can be smaller
than the linear prediction by a factor of three. Finally, when applied to neutrinos, we findthat neutrino perturbations deviate significantly from linear perturbations even below thefree-streaming scales, and thus neutrinos cannot be treated as linear perturbations

Strong CP problem and cosmological constant
Fuminobu Takahashi
IPMU
We point out that the long-standing strong CP problem may be resolved by an anthropic
argument. The key ideas are: (i) to allow explicit breaking(s) of the Peccei-Quinn symmetry
which reduces the strong CP problem to the cosmological constant problem, and (ii) toconjecture that the probability distribution of the vacuum energy has a mild pressure
towards higher values. The cosmological problems of the (s)axion with a large PecceiQuinn scale are absent in our mechanism, since the axion acquires a large mass from theexplicit breaking.

Testing dark energy models: possible complications and some issues of darkenergy perturbations
Tomo Takahashi
Saga University
We discuss the issue of testing dark energy models, paying particular attention to somepossible complications when one takes into account an uncertainty in other cosmologicalaspects. After discussing theoretical aspects of some dark energy models, we investigate
the possibilities of testing some models, in particular, the cosmological constant, with
future cosmological observations such as CMB, SNeIa and so on. In addition, weinvestigate the issue of dark energy perturbations. Since it is possible that some different
models of dark energy can give an almost identical cosmological background evolution,
the study of dark energy perturbations would be interesting. We study possible signaturesof dark energy perturbations and discuss its implications for tests of dark energy models.

Can we rule out unified dark matter models?
Yuko Urakawa
Waseda University
We investigate the observational signatures of Unified Dark Matter (UDM) models, inwhich a scalar field behaves both as dark matter and as dark energy. It is known that inmost of UDM models, the Jeans instability disappears after the transition to the present
acceleration era and therefore the power spectrum of the Large Scale Structure shows aproblematic behavior. Recently, however, several UDM models described by a scalar fieldwith a non-canonical kinetic term are shown to predict the power spectrum which is ingood agreement with SDSS data. Computing weak lensing spectra and the Integrated
Sachs-Wolfe effect, we study in more detail the observational signitures of these models
and discuss whether such UDM models are viable or not.

Dark energy, Finite-mass Neutrino, and Primordial Magnetic Field
Dai G. Yamazaki
Institute of Astronomy and Astrophysics, Academia Sinica
Placing constraints on the neutrino mass is an important goal in modern physics. Recently
an upper limit of neutrino mass is constrained less than 1 eV order by kinematical researchas tritium beta decay experiments and cosmological observations. On the other hand,
Magnetic fields have been observed in clusters of galaxies with strength of 0.1-1.0 ~ \\mu
G. One possible explanation for such magnetic fields in galactic clusters is the existence ofa primordial magnetic field (PMF) of order 1 nG whose field lines collapse as structure
forms. In this presentation, we show effects of the PMF on the cosmic microwave

background and the matter power spectrum with finite-neutrinos, and discuss influences of
the PMF and finite-neutrinos in the constraint on the dark energy from cosmologicalobservations.