M.Sc. (Tribhuvan
Univ), Ph.D. (Seoul Nat'l Univ)
Royal Society University
Fellow
My research has centred on the exploration of phenomena
at the
interface of gravitation, cosmology, astrophysical and superstring
theory. It
underpins fundamental studies on theories of early Universe inflation,
braneworld compactifications, cosmological solutions of supergravity
and superstring
theories, models of dark energy and modified gravity, and black hole
physics.
I
plan to continue the investigation of this rich arena.
My publication list contains links to online versions of my papers from
the SLAC archive (citation
list)
I've
been fortunate to pursue my work on
String cosmology, modern Kaluza-Klein theories, quantum
gravity and black holes, extra dimensions and braneworld models,
dark energy and Gauss-Bonnet cosmologies, particle cosmology and
large-scale
structure of the Universe
What I lectured in the past
Undergraduate Courses:
Classical Electrodynamics, Mathematical Physics, Quantum Mechanics (I
and II)
Relativistic Quantum Mechanics (Phys420)
Electrodynamics
Graduate Courses:
General Relativity
General Relativity and Cosmology
Current Teaching:
Nuclear and Particle Physics (Phys310)
Classical Mechanics and Symmetry Principle (Phys326)
Research Interests:
Implications of
string theory to
inflation
and dark energy models
Classical
supergravities
and time-dependent Solutions
Cosmology with
extra dimensions
(warped compactifications)
Inflation and
cosmological perturbations
Quantum
gravity (black holes, gravity/gauge theory duality)
How to
contact me (Contact
Details)
Postal address: Department of Physics and Astronomy University of
Canterbury, Private Bag 4800, Christchurch, New Zealand
Phone: +64 3 364-2987 Ex 7559, Fax: +64 3 364 2469
mailto: ishwaree.neupane@canterbury.ac.nz, and ipn977@gmail.com
Experience and Appointment:
Senior Research
Associate, Nov 2009 --
to date
FoRST
Research Fellow,
University
of Canterbury, July 2006 - Oct 2009
Visiting Fellow,
CERN Theory Division, July 15 - Sept 15, 2006, Geneva.
Postdoctoral
Research and Teaching Associate,
Canterbury University,
July 2004 - June 2006
Regular
Associate,
2004-2009, Abdus Salam ICTP,
Trieste, Italy
Visiting
Fellow,
CERN Theory Division, March 24-May 23, 2004, Geneva.
Visiting
Fellow,
Sept 20 - Nov. 12, 2003, The Abdus Salam ICTP,
Trieste, Italy.
Research
visitor,
July 14- August 15 (2003), KEK/HEP Theory Division,
Tsukuba, Japan.
Postdoctoral
Fellow,
September 2002- July 2004, Department of
Physics, NTU, Taipei 106, Taiwan.
Visiting
Fellow,
March 2002 - August 2002, Abdus Salam ICTP and Physics
Department, CERN Theory group
Visiting
Research
Associate,
Aug. 2000 - March
2001, Dept. of Physics,
University of Waterloo, Canada.
Research
Assistant:
Aug. 1998 - Feb. 2002, Seoul National University.
Program
Coordinator
(Science Stream) at Littel Angels' College, June 1997- Feb 1998
Lecturer,
June 1997 -- , Central Department of Physics (CDP),
Tribhuvan University, Kathmandu
Editorial
Board
Member -
Nepal Physical Society, July 1995 - July 1997
Assistant
Lecturer,
July 1994 - June 1997
Life
Member:
Nepal Physical Society
Awards and Honors:
2009 - Marsden funded
fast-start research grant, Royal Society of NZ
2007 - Elizabeth Ellen Dalton
Award from FoRST, New Zealand
2006 - FoRST (Foundation for Research, Science and
Techinology)
Research Grants (2006)
2004- Mardsen funded
postdoctoral fellowship
2002- NSC Fellowship for
Postdoctoral Research, Taiwan (2002)
2002- Awarded for best PhD
thesis research (1 million KW), Seoul
National University.
2000-2002 - Brain Korea 21
Award (for 2 yrs), Seoul National University
(2001)
1998-2002 Seoam Fellowship for
PhD program (4 years), South Korea,
(Nov. 1997)
1990-1992 Graduate Admission
Tuition Award, Tribhuvan University (1990)
1989-1991 Best High School
Physics/Math Teacher Award (1991)
1986-1988 Intelligent Student
Award, Amrit Campus, Tribhuvan University
(1987)
______________________________________________________________________
Selected Publication:
I.P. Neupane, Nuclear Physics B [arXiv:1011.
5007]
``Warped compacification to de Sitter
space''.
I.P. Neupane, Physics Letters B [arXiv:0903.4190]
``Extra dimensions, warped compactifications
and cosmic acceleration''.
I.P. Neupane (with Ben Leith), JCAP :0705, 019 (2007) [arxiv:hep-th/0702002]
``Gauss-Bonnet cosmologies:
crossing the phantom divide and the transition from matter dominance to dark energy,''
I.P. Neupane, Phys. Rev. Lett. 98: 061301,2007 [arxiv:hep-th/0609086]
"Accelerating Universes from
Compactification on a Warped Conifild"
I.P. Neupane (with B. Carter) J. Cosmology and Astroparticle Physics,
JCAP 0606:004,2007
"Towards
inflation and dark
energy cosmologies from modified Gauss-Bonnet theory" [arxiv:hep-th/0512262]
I.P. Neupane (with D.L. Wiltshire) Physical Review D72:083509, 2005
``Cosmic
acceleration from M-theory on twisted spaces,"
[arxiv:hep-th/0504135]
I. P. Neupane (with C.-M. Chen, P.-M. Ho, J.E. Wang, and N.
Ohta) JHEP:
0310 (2003) 058
[arXiv:hep-th/0306291]
``Hyperbolic
Space Cosmologies''
I. P. Neupane, Phys. Rev. D 67
(2003) 061501(R) [arXiv:hep-th/0212092]
``Black hole entropy in
string-generated gravity models''
I. P. Neupane (with Y. M. Cho), Phys. Rev. D 66 (2002) 024044
[arXiv:hep-th/0202140],
``Anti-de Sitter Black Holes, Thermal
Phase Transitions and Holography
in Higher Curvature Gravity''
I. P. Neupane (with Y.M. Cho and P. S. Wesson), Nucl. Phys. B621 (2002)
388-412 [arXiv:hep-th/0104227]
``No ghost states of Gauss-Bonnet
interaction in warped backgrounds''
I. P. Neupane, JHEP:0009 (2000)
040 [arXiv:hep-th/0008190]
``Consistency of Higher Derivative
Gravity in the Brane Background''
Selected Conference Proceedings:
I. P. Neupane, Book Chapter
Dark Energy and Dark Matter in Models
with Warped Extra Dimensions,
Invited Contribution to the Proceedings of the Dark Mater 2009,
Christchurch, Jan 2009, New Zealand, eds
H.V. Klapdor-Kelingrothaus (World Scientific, Singapore, 2009).
I. P. Neupane, [arXiv:0904.4805]
Black Holes, Entropy Bound and
Causality Violation,
Invited contributions to the Proceedings of the International
Conference in Astrophysics, Particle Physics and
Quantum Field Theory: 75 Years since Solvay, Nov 2008, (World
Scientific, 2009) pp 3584-3591
I. P. Neupane,
Constraints on Gauss-Bonnet Dark
Energy Cosmologies, World Scientific,
Invited Contribution, Dark Mater 2007, Sydney, Sept 2007, eds H.V.
Klapdor-Kelingrothaus and
G.F. Lewis (World Scientific, Singapore, 2008) pp 228-242.
I. P. Neupane, ``Towards
inflation and dark energy cosmologies in string generated string models,'',
Proceedings of XXXXI de Moriond Meeting, March 19-25, 2006, La Tuile,
Italy, 8pp [arxiv:hep-th/0605265]
I. P. Neupane, ``Dark Energy and
Cosmic Acceleration: M theory
perspectives'',
Proceedings of XXXIX de Moriond Meeting, April 1-4, 2004, La Tuile,
Italy
I. P. Neupane, ``Cosmic Acceleration
and M Theory Cosmology'',
Proceedings of 2003 International Symposium on Cosmology and Particle
Astrophysics
(CosPA 2003), Taipei, 13-15 Nov 2003.
I.P. Neupane, ``Inflation from
string/M theory compactification?'',
Lattice 2003, 800-802 (Tsukuba 2003)
I. P. Neupane, ``AdS/CFT, Large N and
Confinement''
Proceedings of Confinement 2003, July 21-24, 2003, RIKEN, Japan,
World Scientific Publishing (2003).
I. P. Neupane, ``Large N Effects on
Thermal Phase Transition'',
ICTP Preprint, IC/02/072 (also at TH2002, Paris)
________________________________________________________________________________________
The Past ...
I
was born in Bharatpur (Chitwan), a town in the middle-South of Nepal.
Chitwan is best known for Narayanghat, a historical trade center by the
bank of
the Narayani river. However, there are at least two other landmarks in
Chitwan.
One is its world-famous Royal
Nepal Chitwan
National Park and
the
second is the unsurpassed diversity of people who represent all 75
districts of
the country, giving it Chitwan its nickname as the 76th district!
I grew
up in Chitwan where I spent the first eighteen years of my life. I regularly visit home since my parents and
sisters still live there, and, of course, to see
friends/relatives.
I
did my Intermediate in Science (I.Sc.) from Rampur Science Campus,
Chitwan, and
B.Sc. (Maths/Physics/Statistics) from Amrit
Science College,
Kathmandu. The College is among the
best in
the country for science
After
completing my B.Sc., I worked as a high school teacher (Math/Science)
at Small
Heaven Secondary English
Boarding School, now
part of Little Angles' College, in Chitwan for about two years. In 1990
I
joined the Central Department of Physics at Tribhuvan
University, Kirtipur, Kathmandu, to pursue my M.Sc. in physics.
After
completing M.Sc. (with dissertation), I started to work as
an
Assistant Lecturer at the same department, Central Department of
Physics (CDP),
from June 1994. In early 1997 my position there turned into a
lectureship. The
department was great and
I made some of my best friends anywhere while I was there, many of them
are now north America.
I had a really wonderful time at CDP. Most importantly, during my
third
year on the job at CDP I met Manju, now my wife, who was
introduced to me
by my best friend. We were engaged three months after we met, and
married a
month later.
In 1997 June I was about to enter Univ of Durham as a
Ph.D.
student, but could not make it after the sudden death of Prof. E.
Squirres there. Later in early 1998 I entered the Ph.D. Program of Seoul National
University, the best
known
university in South
Korea,
as a SeoAM fellow, the most prestigious award given to a foreign
student.
It was fascinating but very odd to move to a different country on my
own, but I
had a really wonderful time at Seoul.
The department was great, I loved Seoul,
and I also made some of my best Korean friends there. I really
appreciate the Physics Department of SNU and its leading role in
frontier research and innovation.
In 2000, I was at the Univ of Waterloo, Canada, for about a year with a
research grant from BK21 (Brain Korea
21st Century) project of the Ministry of Education, South Korea.
In late 2001, my time
at SNU was up when I graduated with a Ph.D. in physics. I then accepted
short visits
of 3 months each at the Abdus
Salam International
Center for Theoretical Physics
(ASICTP) and Physics Department, Theory Division, CERN, Geneva. I went
to Taipei
in September 2002 as a postdoctoral research fellow at the National Taiwan
University, the best
university in Taiwan.
It was
an interesting/wonderful
experience for us, and I wrote some of my well-cited
papers there.
In June 2004, I joined the university of canterbury as a
Royal Society University Postotoral Fellow, worked as a FoRST
(Foundation) Fellow from June 2006 to Oct 2009.
Since Nov 2009 I have been a Royal Society University Fellow.
Family:
Married: 31 May 1997 to Manju Pokharel
Children: Imas, born 5 Sept 1999; Iros born 4 July 2002
My research: Past and Present
For my research work at UC, I am supported by the Marsden Fund of the
Royal Society of New Zealand.
Broadly, my research concerns the interplay between gravitation and
particle
physics in the very early universe. More precisely, I am interested in
the
cosmological implications of quantum field theories, general
relativity, and
M/superstring theories. I find some particular interests in cosmology
with
extra dimensions and their effective applications to the study of early
universe cosmology, including primordial inflation and dark energy
models. My
parallel interests have been in the study of brane world physics, the
higher
dimensional black holes, and the duality between gravity in AdS space
and
conformal field theories.
My interests are also in the interface between observational and
theoretical
cosmology; more specifically, the nature and origin of Dark
Energy and Dark Matter,
the theory
of cosmic inflation and the observational tests for alternative
theories of
gravity.
My past research work falls into three categories:
I. Extra dimensions and
Braneworld compactifications
II. Black holes in higher derivative gravity theories
III. Inflation/accelerating cosmologies from M/superstring
theories
I. Extra dimensions and brane-world cosmology
One of the radical views in physics is that our observable universe may
be a
four-dimensional hypersurface (a 3-brane) embedded in a higher
dimensional
space-time with various possible compactifications and background
geometries, such as, fluxes and branes in the extra dimensions.
Interestingly, the constraints on the brane-world scenarios, with
warped extra
dimension(s), appear less stringent than those on ordinary
Kaluza-Klein
theories. One such example is that the corresponding extra dimensions
may be
significantly large.
In 1999, Randall and Sundrum (RS) showed that it is possible to take a
limit of
their theory in which the fifth dimension runs over an infinite value,
but its
volume is still finite. This translates into a much larger allowed
volume for
the extra dimensions. It was subsequently known that branes can
localize
the Standard Model degrees of freedom, including gravity. Then, as in
traditional Kaluza-Klein theories, it is necessary that all dimensions
other
than those we observe be compactified/warped, so that their existence
does not
conflict with experimental data. The difference in the new scenarios is
that,
since standard model fields do not propagate in the extra dimensions,
it is
only necessary to evade constraints on higher-dimensional gravity, and
not, for
example, on higher-dimensional electromagnetism. This is important,
since
electromagnetism has been tested to great precision down to extremely
small
scales, while the microscopic tests of gravity are not yet precise.
Brane world idea is intriguing not only because Einstein gravity is
recovered
on the brane, but it also relates AdS space (the domain of gravity
favorable to
string/M theory) to Friedmann-Roberton-Walker (FRW) cosmology on the
brane,
other than providing a new avenue for thinking about gravity in extra
dimensions. The original RS brane model can be extended to a
co-dimension 2
construction in which our 3-brane is localized at the intersection of
two or
more branes, including possible curvature corrections, which I have
established
in
JHEP:0009 (2000) 040 [arXiv:hep-th/0008190], ``Consistency of Higher
Derivative
Gravity in the Brane Background''.
In this work, one of my well-cited papers, I have studied brane-world
models by
introducing curvature corrections in a Gauss-Bonnet form, and more
precisely,
discussed on consistency of low energy string effective actions in the
brane
background (i.e. with a warped extra dimension).
Later in the following two papers,
I. P. Neupane, Phys. Lett. B512 (2001) 137-145
[arXiv:hep-th/0104226]
``Gravitational potential correction with Gauss-Bonnet interaction''
I. P. Neupane (with Y.M. Cho and P.S. Wesson), Nucl. Phys. B621
(2002)
388-412 [arXiv:hep-th/0104227]
``No ghost states of Gauss-Bonnet interaction in warped backgrounds''
I have shown how one can recover a localized Einstein gravity in the
presence of
higher curvature terms in GB form. In
I. P. Neupane, Class. Quantum Gravity,
19
(2002) 5507-5523 [arXiv:hep-th/0106100]
``Completely localized gravity with higher curvature terms''
I. P. Neupane (with Y. M. Cho), Int. J. Mod. Phys. A18 (2003)
2703 [arXiv:hep-th/0112227],
``Warped Brane-World Compactification with a Gauss-Bonnet Term''
I further extended our earlier work by explicitly constructing
intersecting
brane-world configurations in arbitrary D dimensions with a GB term.
Interestingly, it was then understood that the Gauss-Bonnet type
curvature
corrections to brane-world action
accommodate a non-trivial brane tension (or positive cosmological
constant) in
higher dimensional scenarios, where gravity is localized to the
intersections
of branes, independently of the co-dimension of our world.
II. Quantum gravity and black holes in higher derivative
gravity
theories
I have studied higher dimensional black holes in AdS space by taking
into
account the possible quadratic curvature corrections, as it help to
explore the
physics of a boundary field theory (or FRW type cosmology on the
brane), next
to leading order, and is discussed in
I. P. Neupane (with Y. M. Cho), Phys. Rev. D 66 (2002) 024044
[arXiv:hep-th/0202140]
``Anti-de Sitter Black Holes, Thermal Phase Transitions and
Holography in
Higher Curvature Gravity''
In the following two papers, I computed free energy and entropy using
Euclidean
action and studied the effects of higher curvature couplings on a
Hawking-Page
type phase transition, and the thermodynamic and gravitational
stability of
higher dimensional black holes in AdS spaces.
I. P. Neupane, Phys. Rev. D 69 (2004) 084011
[arXiv:hep-th/0302132]
``Thermodynamic and Gravitational Instability on Hyperbolic Spaces''
I. P. Neupane, Phys. Rev. D 67 (2003) 061501(R)
[arXiv:hep-th/0212092]
``Black hole entropy in string-generated gravity models''
It was found that topological/hyperbolic black holes can be
thermodynamically
stable only if the (extremal) entropy and specific heat are
non-negative for
the background. It would be interesting to extend this work by studying
some
other aspects of higher-dimensional (anti-) de Sitter black holes by
introducing charges and/or rotation parameters, and analyse possible
relations
between the quasi-normal modes and the black hole entropy in such
theories.
Black holes with non-zero rotation parameters are really intriguing as
they
could thermodynamically and gravitational be more stable compared those
with no
rotation. My recent work in this direction is
I. P. Neupane (with B.M.N.
Carter) , Phys.Rev.D72:043534,2005
Thermodynamic and Stability of Higher Dimensional Rotating
(Kerr) AdS
black holes, [arXiv: gr-qc/0506103]
III. Inflation and Accelerating Cosmologies from string/M Theory
Cosmology is perhaps the only arena in which string/M theory and hence
the
existence of extra dimensions is testable. A second benefit of
cosmology is its
unique ability to probe matter under extremes of density and
temperature that
can never be achieved in laboratories on Earth. For decades, a central
issue in
cosmology was to figure out what happened to the expansion of the
universe at
the early epoch. It is well established that the expansion rate of our
universe
would always be slowing down. This is because gravity is attractive,
and the
mutual attraction between all the galaxies in the universe acts to slow
the
expansion. In turn, the accelerated expansion of our universe would
eventually
stop and the universe starts to decelerates (that is, de Sitter stage
can be
transient at best).
The recent data from type Ia supernovae and WMAP, however,
showed/confirmed the
first evidence that the universe is actually accelerating and about
two-third
of the total energy density comes from dark energy! This evidence has
since
become very firm and presents an immense challenge to fundamental
theories such
as string/M theory and their low energy supergravity limits. What could
be
causing this? Although the universe is currently accelerating,
inflation can
take place into the future only if vacuum-energy (or other sufficiently
slowly
red-shifting source of energy density) dominates the energy density of
a region
of physical radius 1/H.
To understand this, we found some particular interests in string theory
compactifications which naturally generate a positive scalar potential
in four
dimensions, so as to describe an accelerated expansion of our universe,
including inflation in the early universe. Of course, a realization of
four-dimensional cosmology from the compactification of higher
dimensional
gravities (such as, string/M theory in 10/11 dimensions) is important
for some
obvious reasons, such as, the existence of extra dimensions and
the
creation of standard model fields/matters from pure gravity. My recent
works have
focused on the issues of cosmic acceleration (and its asoociated dark
energy
problem) from a cosmological (time-dependent) compactification of such
theories. In the following work
I. P. Neupane (with Chiang-Mei Chen, Pei-Ming Ho, and John Wang)
[arXiv:hep-th/0304177].
``A Note on Acceleration from Product Space Compactifications,''
JHEP: 0307
(2003) 017
we have shown how a period of accelerating expansion of our universe
can arise
from cosmological compactification of classical supergravities on
product
spaces of time-varying volume, generalizing an earlier work by Townsend
and
Wohlfarth (hep-th/0303097). This and similar other approaches might
allow us to
eliminate the need for cosmological constant, replacing it with
slowly
varying scalars (moduli) associated with the compactified extra
dimensions. In
a subsequent work
Chiang-Mei Chen, Pei-Ming Ho, I.P. Neupane, N. Ohta, and John Wang,
``Hyperbolic Spaces Cosmologies'' JHEP: 0310
(2003) 058
[arXiv:hep-th/0306291]
where we were joined by N. Ohta, we have pursued a more general and
systematic
study of time-dependent supergravity solutions on product spaces
without or
with background (electric or magnetic) fluxes. These are fresh
perspectives on
the problem of explaining the early universe cosmology and/or late-time
acceleration with time-varying scale factors of internal spaces,
which
dynamically generate a non-zero 4d effective potential. This work
explores on
the simplest possibility of obtaining accelerating cosmologies from
compactification. There are some interesting field theoretic issues
that we
would like answer further, such as the mass (or energy) spectrum,
dynamical stabilization of the size of extra dimensions, and
realization of the
Standard Model physics from warped/flux compactifications.
In late 2003, by studying an effective cosmological model arising from
compactifications 11d supergravity in time-dependent background, which
includes
the effects of background fields other than a non-trivial curvature of
the
internal space,
I.P. Neupane, Class.Quantum Grav. 19 (2004) 4383
[arXiv:hep-th/0311071]
``Accelerating Cosmologies from Exponential Potentials''
I have shown that an exponential potential of string/M-theory origin
could
explain a period of accelerated expansion of a four-dimensional flat
(or open)
FRW universe, putting some constraints on the parameters
involved.
Recently, David L. Wiltshire and I were working into this problem. We
made some
progresses in this direction by considering extra dimension with
``certain twists"
in the geometry.
I.P. Neupane (with D.L. Wiltshire) Phys. Lett. B 619: 201,2005
[arXiv:hep-th/0502003]
``Accelerating cosmologies from compactification with a twist"
This indeed provides a new avenue in the direction of getting inflation
or
accelerating cosmologies from compactifications on Ricci-flat internal
spaces.
The effects of background fluxes (and/or twists) and branes, other than
that
of internal compact spaces, might be relevant to realise/contruct
any
realistic inflationary type potential in four dimensions and finally to
realize
a cosmological model of our universe. We look forward to find an
economical way
of unifying two seemingly separate puzzles in contemporary particle
physics and
cosmology: Dark Energy and Cosmic Acceleration.