Faculty
Publications added in October, 2009
Query
Results from the Smithsonian/NASA
Astrophysics Data System (ADS)
The
following are Harvard Physics faculty members' publications,
added to the ADS database last month. Please note that
some publications which appeared in print last month
may not be included in the database (and therefore may
not appear on this list) until the following month.
| Title: |
What Should We Expect
Students to Learn? |
| Authors: |
Finkelstein, Noah; Mazur, Eric; Lasry, Nathaniel |
| Publication: |
The Physics Teacher,
Volume 47, Issue 8, pp. 484-484 (2009). (PhTea
Homepage) |
| Publication
Date: |
11/2009 |
| Origin: |
AIP |
| Keywords: |
physics education,
educational technology, societies, problem solving,
teaching |
| PACS Keywords: |
Research in physics
education, Science and society |
| Abstract
Copyright: |
(c) 2009: American
Institute of Physics |
| DOI: |
10.1119/1.3246459 |
| Bibliographic
Code: |
2009PhTea..47..484F |
Abstract
A rejoinder to Sobel's comment on "Are most people
too dumb for physics?" We read Michael Sobel's response
with much interest and appreciate his enthusiasm and
commitment to physics education. Yet, we continue to
find that our goals and methods differ markedly. Foremost,
because we do not agree that physics is a "different
category" of hard which is accessible to a select
few (i.e.,
"a certain sort of very bright student"'),
we cannot agree that ordinary, nonscience students must
be taught a different kind of physics. We object to the
idea of two "types"' of physics-one for the
layperson and one for the specialist. Physics must have
relevance for everyone.
Abstract
We report nanoscale patterning of graphene using a helium
ion microscope configured for lithography. Helium ion
lithography is a direct-write lithography process, comparable
to conventional focused ion beam patterning, with no
resist or other material contacting the sample surface.
In the present application, graphene samples on Si/SiO2
substrates are cut using helium ions, with computer controlled
alignment, patterning, and exposure. Once suitable beam
doses are determined, sharp edge profiles and clean etching
are obtained, with little evident damage or doping to
the sample. This technique provides fast lithography
compatible with graphene, with ~15 nm feature sizes.
| Title: |
Repetitive Readout
of a Single Electronic Spin via Quantum Logic
with Nuclear Spin Ancillae |
| Authors: |
Jiang, L.; Hodges, J. S.; Maze, J. R.; Maurer, P.; Taylor, J. M.; Cory, D. G.; Hemmer, P. R.; Walsworth, R. L.; Yacoby, A.; Zibrov, A. S.; Lukin, M. D. |
| Publication: |
Science, Volume 326,
Issue 5950, pp. 267- (2009). |
| Publication
Date: |
10/2009 |
| Category: |
PHYSICS |
| Origin: |
SCIENCE |
| Abstract
Copyright: |
(c) 2009: Science |
| DOI: |
10.1126/science.1176496 |
| Bibliographic
Code: |
2009Sci...326..267J |
Abstract
Robust measurement of single quantum bits plays a key
role in the realization of quantum computation and communication
as well as in quantum metrology and sensing. We have
implemented a method for the improved readout of single
electronic spin qubits in solid-state systems. The method
makes use of quantum logic operations on a system consisting
of a single electronic spin and several proximal nuclear
spin ancillae in order to repetitively readout the state
of the electronic spin. Using coherent manipulation of
a single nitrogen vacancy center in room-temperature
diamond, full quantum control of an electronic-nuclear
system consisting of up to three spins was achieved.
We took advantage of a single nuclear-spin memory in
order to obtain a 10-fold enhancement in the signal amplitude
of the electronic spin readout. We also present a two-level,
concatenated procedure to improve the readout by use
of a pair of nuclear spin ancillae, an important step
toward the realization of robust quantum information
processors using electronic- and nuclear-spin qubits.
Our technique can be used to improve the sensitivity
and speed of spin-based nanoscale diamond magnetometers.
| Title: |
Are Most People Too
Dumb for Physics? |
| Authors: |
Lasry, Nathaniel; Finkelstein, Noah; Mazur, Eric |
| Publication: |
The Physics Teacher,
Volume 47, Issue 7, pp. 418-422 (2009). (PhTea
Homepage) |
| Publication
Date: |
10/2009 |
| Origin: |
AIP |
| Keywords: |
physics education,
educational courses, educational technology,
socio-economic effects, problem solving, mathematics |
| PACS Keywords: |
Science and society,
Course design and evaluation, Research in physics
education |
| DOI: |
10.1119/1.3225498 |
| Bibliographic
Code: |
2009PhTea..47..418L |
Abstract
Not Available
| Title: |
Evidence for the ηb(1S)
Meson in Radiative Υ(2S) Decay |
| Authors: |
Aubert, B.; Bona, M.; Karyotakis, Y.;... Morii, M.;...
and 482 coauthors. |
| Publication: |
Physical Review Letters,
vol. 103, Issue 16, id. 161801 (PhRvL
Homepage) |
| Publication
Date: |
10/2009 |
| Origin: |
APS |
| PACS Keywords: |
Decays of J/psi, Upsilon,
and other quarkonia, Mesons with S=C=B=0, mass>2.5
GeV, Bottom quarks |
| Abstract Copyright: |
(c) 2009: The American
Physical Society |
| DOI: |
10.1103/PhysRevLett.103.161801 |
| Bibliographic
Code: |
2009PhRvL.103p1801A |
Abstract
We have performed a search for the η
b(1S)
meson in the radiative decay of the Υ(2S) resonance using
a sample of 91.6×10
6 Υ(2S) events recorded
with the BABAR detector at the PEP-II B factory at the
SLAC National Accelerator Laboratory. We observe a peak
in the photon energy spectrum at E
γ=609.3
-4.5+4.6(stat)±1.9(syst)MeV,
corresponding to an η
b(1S) mass of 9394.2
-4.9+4.8(stat)±2.0(syst)MeV/c
2.
The branching fraction for the decay Υ(2S)→γη
b(1S)
is determined to be [3.9±1.1(stat)
-0.9+1.1(syst)]×10
-4.
We find the ratio of branching fractions B[Υ(2S)→γη
b(1S)]/B[Υ(3S)→γη
b(1S)]=0.82±0.24(stat)
-0.19+0.20(syst).
Abstract
We report repeated single-shot measurements of the two-electron
spin state in a GaAs double quantum dot. The readout
allows measurement with a fidelity above 90% with a ˜7μs
cycle time. Hyperfine-induced precession between singlet
and triplet states of the two-electron system are directly
observed, as nuclear Overhauser fields are quasistatic
on the time scale of the measurement cycle. Repeated
measurements on millisecond to second time scales reveal
the evolution of the nuclear environment.
| Title: |
Precision Measurement
of the X(3872) Mass in J/ψπ+π- Decays |
| Authors: |
Aaltonen, T.; Adelman, J.; Akimoto, T.;
... Franklin, M.;
... Guimaraes da Costa, J....;
and 598 coauthors. |
| Publication: |
Physical Review Letters,
vol. 103, Issue 15, id. 152001 (PhRvL
Homepage) |
| Publication
Date: |
10/2009 |
| Origin: |
APS |
| PACS Keywords: |
Mesons with S=C=B=0,
mass>2.5 GeV, Glueball and nonstandard multi-quark/gluon
states, Decays of J/psi, Upsilon, and other quarkonia |
| Abstract Copyright: |
(c) 2009: The American
Physical Society |
| DOI: |
10.1103/PhysRevLett.103.152001 |
| Bibliographic
Code: |
2009PhRvL.103o2001A |
Abstract
We present an analysis of the mass of the X(3872) reconstructed
via its decay to J/ψπ
+π
- using
2.4fb
-1 of integrated luminosity from p&pmacr;
collisions at s=1.96TeV, collected with the CDF II detector
at the Fermilab Tevatron. The possible existence of two
nearby mass states is investigated. Within the limits
of our experimental resolution the data are consistent
with a single state, and having no evidence for two states
we set upper limits on the mass difference between two
hypothetical states for different assumed ratios of contributions
to the observed peak. For equal contributions, the 95%
confidence level upper limit on the mass difference is
3.6MeV/c
2. Under the single-state model the
X(3872) mass is measured to be 3871.61±0.16(stat)±0.19(syst)MeV/c
2,
which is the most precise determination to date.
| Title: |
Observation of the Ωb- baryon
and measurement of the properties of the Ξb- and Ωb- baryons |
| Authors: |
Aaltonen, T.; Adelman, J.; Akimoto, T.;
... Franklin, M.;
... Guimaraes da Costa, J....;
and 597 coauthors. |
| Publication: |
Physical Review D,
vol. 80, Issue 7, id. 072003 (PhRvD
Homepage) |
| Publication
Date: |
10/2009 |
| Origin: |
APS |
| PACS Keywords: |
Hadronic decays, Baryon
production, Bottom baryons |
| Abstract Copyright: |
(c) 2009: The American
Physical Society |
| DOI: |
10.1103/PhysRevD.80.072003 |
| Bibliographic
Code: |
2009PhRvD..80g2003A |
Abstract
We report the observation of the bottom, doubly-strange
baryon
Ω
b- through the decay chain
Ω
b-→J/ψΩ
-,
where J/ψ→μ
+μ
-,
Ω
-→ΛK
-, and
Λ→pπ
-, using 4.2fb
-1 of
data from p&pmacr; collisions at s=1.96TeV, and recorded
with the Collider Detector at Fermilab. A signal is observed
whose probability of arising from a background fluctuation
is 4.0×10
-8, or 5.5 Gaussian standard deviations.
The Ω
b- mass is measured to
be 6054.4±6.8(stat)±0.9(syst)MeV/c
2. The lifetime
of the Ω
b- baryon is measured
to be 1.13
-0.40+0.53(stat)±0.02(syst)ps.
In addition, for the Ξ
b- baryon
we measure a mass of 5790.9±2.6(stat)±0.8(syst)MeV/c
2 and
a lifetime of 1.56
-0.25+0.27(stat)±0.02(syst)ps.
Under the assumption that the Ξ
b- and
Ω
b- are produced with similar
kinematic distributions to the Λ
b0 baryon,
we find (σ(Ξ
b-)B(Ξ
b-→J/ψΞ
-))/(σ(Λ
b0)B(Λ
b0→J/ψΛ))=0.167
-0.025+0.037(stat)±0.012(syst)
and (σ(Ω
b-)B(Ω
b-→J/ψΩ
-))/(σ(Λ
b0)B(Λ
b0→J/ψΛ))=0.045
-0.012+0.017(stat)±0.004(syst)
for baryons produced with transverse momentum in the
range of 6–20GeV/c.
| Title: |
Search for the Higgs
boson produced in association with Z→ℓ+ℓ- using
the matrix element method at CDF II |
| Authors: |
Aaltonen, T.; Adelman, J.; Akimoto, T.;
... Franklin, M.;
... Guimaraes da Costa, J....;
and 596 coauthors. |
| Publication: |
Physical Review D,
vol. 80, Issue 7, id. 071101 (PhRvD
Homepage) |
| Publication
Date: |
10/2009 |
| Origin: |
APS |
| PACS Keywords: |
Standard-model Higgs
bosons, Decays of Z bosons, Inclusive production
with identified leptons, photons, or other nonhadronic
particles, Z bosons |
| Abstract Copyright: |
(c) 2009: The American
Physical Society |
| DOI: |
10.1103/PhysRevD.80.071101 |
| Bibliographic
Code: |
2009PhRvD..80g1101A |
Abstract
We present a search for associated production of the
standard model Higgs boson and a Z boson where the Z
boson decays to two leptons and the Higgs decays to a
pair of b quarks in p&pmacr; collisions at the Fermilab
Tevatron. We use event probabilities based on standard
model matrix elements to construct a likelihood function
of the Higgs content of the data sample. In a CDF data
sample corresponding to an integrated luminosity of 2.7fb
-1 we
see no evidence of a Higgs boson with a mass between
100GeV/c
2 and 150GeV/c
2. We set
95% confidence level upper limits on the cross section
for ZH production as a function of the Higgs boson mass
m
H; the limit is 8.2 times the standard model
prediction at m
H=115GeV/c
2.
Abstract
It has been predicted that the phase sensitive part of
the current through a non-Abelian ν=5/2 quantum Hall
Fabry-Perot interferometer will depend on the number
of localized charged e/4 quasiparticles (QPs) inside
the interferometer cell. In the limit where all QPs are
far from the edge, the leading contribution to the interference
current is predicted to be absent if the number of enclosed
QPs is odd and present otherwise, as a consequence of
the non-Abelian QP statistics. The situation is more
complicated, however, if a localized QP is close enough
to the boundary so that it can exchange a Majorana fermion
with the edge via a tunneling process. Here, we derive
an exact solution for the dependence of the interference
current on the coupling strength for this tunneling process,
and confirm a previous prediction that for sufficiently
strong coupling, the localized QP is effectively incorporated
in the edge and no longer affects the interference pattern.
We confirm that the dimensionless coupling strength can
be tuned by the source-drain voltage, and we find that
not only does the magnitude of the even-odd effect change
with the strength of bulk-edge coupling, but in addition,
there is a universal shift in the interference phase
as a function of coupling strength. Some implications
for experiments are discussed at the end.
| Title: |
Electromagnetically
induced transparency with noisy lasers |
| Authors: |
Xiao, Yanhong; Wang, Tun; Baryakhtar, Maria; van Camp, Mackenzie; Crescimanno, Michael; Hohensee, Michael; Jiang, Liang; Phillips, David F.; Lukin, Mikhail D.; Yelin, Susanne F.; Walsworth, Ronald L. |
| Publication: |
Physical Review A,
vol. 80, Issue 4, id. 041805 (PhRvA
Homepage) |
| Publication
Date: |
10/2009 |
| Origin: |
APS |
| PACS Keywords: |
Effects of atomic
coherence on propagation, absorption, and amplification
of light; electromagnetically induced transparency
and absorption, Line shapes, widths, and shifts,
Optical transient phenomena: quantum beats, photon
echo, free-induction decay, dephasings and revivals,
optical nutation, and self-induced transparency |
| Abstract
Copyright: |
(c) 2009: The American
Physical Society |
| DOI: |
10.1103/PhysRevA.80.041805 |
| Bibliographic
Code: |
2009PhRvA..80d1805X |
Abstract
We demonstrate and characterize two coherent phenomena
that can mitigate the effects of laser phase noise for
electromagnetically induced transparency (EIT): a laser-power-broadening-resistant
resonance in the transmitted intensity cross correlation
between EIT optical fields, and a resonant suppression
of the conversion of laser phase noise to intensity noise
when one-photon noise dominates over two-photon-detuning
noise. Our experimental observations are in good agreement
with both an intuitive physical picture and numerical
calculations. The results have wide-ranging applications
to spectroscopy, atomic clocks, and magnetometers.
Abstract
We define a refined topological vertex which depends
in addition on a parameter, which physically corresponds
to extending the self-dual graviphoton field strength
to a more general configuration. Using this refined topological
vertex we compute, using geometric engineering, a two-parameter
(equivariant) instanton expansion of gauge theories which
reproduce the results of Nekrasov. The refined vertex
is also expected to be related to Khovanov knot invariants.
Abstract
Recent work has shown that compactifications of F-theory
provide a potentially attractive phenomenological scenario.
The low energy characteristics of F-theory GUTs consist
of a deformation away from a minimal gauge mediation
scenario with a high messenger scale. The soft scalar
masses of the theory are all shifted by a stringy effect
which survives to low energies. This effect can range
from 0 GeV up to ~ 500 GeV. In this paper we study potential
collider signatures of F-theory GUTs, focussing in particular
on ways to distinguish this class of models from other
theories with an MSSM spectrum. To accomplish this, we
have adapted the general footprint method developed recently
for distinguishing broad classes of string vacua to the
specific case of F-theory GUTs. We show that with only
5 fb‑1 of simulated LHC data, it is possible to distinguish
many mSUGRA models and low messenger scale gauge mediation
models from F-theory GUTs. Moreover, we find that at
5 fb‑1, the stringy deformation away from minimal gauge
mediation produces observable consequences which can
also be detected to a level of order ~ ±80 GeV. In this
way, it is possible to distinguish between models with
a large and small stringy deformation. At 50 fb‑1, this
improves to ~ ±10 GeV.
| Title: |
Wrapped M2/M5 duality |
| Authors: |
Guica, Monica; Strominger, Andrew |
| Affiliation: |
Jefferson Physical
Laboratory, Harvard University, Cambridge, MA
02138, U.S.A. document.write(mkemail("mmguica","","lpthe","jussieu","fr"));mmguica@lpthe.jussieu.fr |
| Publication: |
Journal of High Energy
Physics, Issue 10, pp. 036 (2009). |
| Publication
Date: |
10/2009 |
| Origin: |
IOP |
| DOI: |
10.1088/1126-6708/2009/10/036 |
| Bibliographic
Code: |
2009JHEP...10..036G |
Abstract
A microscopic accounting of the entropy of a generic
5D supersymmetric rotating black hole, arising from wrapped
M2-branes in Calabi-Yau compactified M-theory, is an
outstanding unsolved problem. In this paper we consider
an expansion around the zero-entropy, zero-temperature,
maximally rotating ground state for which the angular
momentum JL and graviphoton charge Q are related by JL2
= Q3. At JL = 0 the near horizon geometry is AdS2 × S3.
As JL2 → Q3 it becomes a singular quotient of AdS3 ×
S2: more precisely, a quotient of the near horizon geometry
of an M5 wrapped on a 4-cycle whose self-intersection
is the 2-cycle associated to the wrapped-M2 black hole.
The singularity of the AdS3 quotient is identified as
the usual one associated to the zero-temperature limit,
suggesting that the (0,4) wrapped-M5 CFT is dual near
maximality to the wrapped-M2 black hole. As evidence
for this, the microscopic (0,4) CFT entropy and the macroscopic
rotating black hole entropy are found to agree to leading
order away from maximality.
Abstract
We have studied the muon neutrino and antineutrino quasi-elastic
(QEL) scattering reactions ( ν μ n→ μ ‑ p and bar{ν }_{μ}ptoμ+n
) using a set of experimental data collected by the NOMAD
Collaboration. We have performed measurements of the
cross-section of these processes on a nuclear target
(mainly carbon) normalizing it to the total ν μ ( bar{ν}_{μ}
) charged-current cross section. The results for the
flux-averaged QEL cross sections in the (anti)neutrino
energy interval 3–100 GeV are < σ_{qel}rangle_{ν_{μ}}=(0.92±0.02(stat)±0.06(syst))×10^{-38}
cm2 and <σ_{qel}rangle_{bar{ν}_{μ}}=(0.81±0.05(stat)±0.09(syst))×10^{-38}
cm2 for neutrino and antineutrino, respectively. The
axial mass parameter M A was extracted from the measured
quasi-elastic neutrino cross section. The corresponding
result is M A =1.05±0.02(stat)±0.06(syst) GeV. It is
consistent with the axial mass values recalculated from
the antineutrino cross section and extracted from the
pure Q 2 shape analysis of the high purity sample of
ν μ quasi-elastic 2-track events, but has smaller systematic
error and should be quoted as the main result of this
work. Our measured M A is found to be in good agreement
with the world average value obtained in previous deuterium
filled bubble chamber experiments. The NOMAD measurement
of M A is lower than those recently published by K2K
and MiniBooNE Collaborations. However, within the large
errors quoted by these experiments on M A , these results
are compatible with the more precise NOMAD value.
| Title: |
Supernovae 2009kb-2009kj |
| Authors: |
Young, D.; Valenti, S.; Rest, A.; Narayan, G.; Huber, M.; Gezari, S.; Rodney, S.; Trundle, C.; Smith, K.; Smartt, S.; Price, P.; Stubbs, C.; Tonry, J.; Riess, A.; Wood-Vasey, W. M.; Botticella, M. T.; Pastorello, A.; Kotak, R.; Fraser, M.; Hunter, D.; Maguire, K.; Foley, R. |
| Publication: |
Central Bureau Electronic
Telegrams, 1988, 1 (2009). Edited by Green, D.
W. E. |
| Publication
Date: |
10/2009 |
| Origin: |
CBAT |
| Objects: |
2009kb-2009kj |
| Bibliographic
Code: |
2009CBET.1988....1Y |
Abstract
D. Young and S. Valenti, Queen's University, Belfast
(QUB); A. Rest and G. Narayan, Harvard-Smithsonian Center
for Astrophysics (CfA); M. Huber and S. Gezari, Johns
Hopkins University (JHU); S. Rodney, Institute for Astronomy
(IfA), University of Hawaii; C. Trundle, K. Smith, and
S. Smartt, QUB; P. Price, IfA; C. Stubbs, CfA; J. Tonry,
IfA; A. Riess, JHU; W. M. Wood-Vasey, University of Pittsburgh;
M. T. Botticella, A. Pastorello, R. Kotak, M. Fraser,
D. Hunter, and K. Maguire, QUB; and R. Foley, CfA, on
behalf of the PS1 Science Consortium, report the discovery
of nine supernovae via the Pan-STARRS Telescope #1 (PS1)
sky survey. Images from PS1 Medium-Deep-Fields 7 and
8 were processed and differenced by the PS1 Image Processing
Pipeline, and detections were filtered with prototype
modules of the Transient Science Server at CfA and QUB.
| Title: |
Discovery and Classification
of Pan-STARRS Transient PS10909010 |
| Authors: |
Huber, M.; Narayan, G.; Berger, E.; Rest, A.; Foley, R.; Wood-Vasey, M.; Riess, A.; Stubbs, C.; Kirshner, R.; Tonry, J.; Price, P. |
| Publication: |
The Astronomer's
Telegram, #2229 |
| Publication
Date: |
10/2009 |
| Origin: |
ATEL |
| Keywords: |
Optical, Novae, Supernovae,
Transients |
| Bibliographic
Code: |
2009ATel.2229....1H |
Abstract
Processing of Pan-STARRS medium-deep field #1 (MD01)
data has led to the discovery of an optical transient,
designated PS10909010, at coordinates RA = 02:28:28.368,
DEC = -04:04:44.08 (J2000) with an apparent brightness
of r~21.5 mag on 2009 September 21 UT. A spectrum of
the source obtained with the GMOS spectrograph on the
Gemini-North 8-m telescope (PI: Berger) on 2009 October
2 UT reveals that the object is a type Ia supernova at
z=0.27 about 3 to 8 days after maximum light.
| Title: |
Coherent population
trapping resonances with linearly polarized light
for all-optical miniature atomic clocks |
| Authors: |
Zibrov, Sergei A.; Novikova, Irina; Phillips, David F.; Walsworth, Ronald L.; Zibrov, Alexander S.; Velichansky, Vladimir L.; Taichenachev, Alexey V.; Yudin, Valery I. |
| Publication: |
eprint arXiv:0910.4703 |
| Publication
Date: |
10/2009 |
| Origin: |
ARXIV |
| Keywords: |
Physics - Atomic
Physics, Physics - Optics |
| Comment: |
7 pages, 7 figures |
| Bibliographic
Code: |
2009arXiv0910.4703Z |
Abstract
We present a joint theoretical and experimental characterization
of the coherent population trapping (CPT) resonance excited
on the D1 line of 87Rb atoms by bichromatic linearly
polarized laser light. We observe high-contrast transmission
resonances (up to 25%), which makes this excitation scheme
promising for miniature all-optical atomic clock applications.
We also demonstrate cancellation of the first-order light
shift by proper choice of the frequencies and relative
intensities of the two laser field components. Our theoretical
predictions are in good agreement with the experimental
results.
Abstract
The Fermi Gamma-Ray Space Telescope reveals a diffuse
inverse Compton signal in the inner Galaxy with the same
spatial morphology as the microwave haze observed by
WMAP, confirming the synchrotron origin of the microwaves.
Using spatial templates, we regress out pi0 gammas, as
well as ICS and bremsstrahlung components associated
with known soft-synchrotron counterparts. We find a significant
gamma-ray excess towards the Galactic center with a spectrum
that is significantly harder than other sky components
and is most consistent with ICS from a hard population
of electrons. The morphology and spectrum are consistent
with it being the ICS counterpart to the electrons which
generate the microwave haze seen at WMAP frequencies.
In addition to confirming that the microwave haze is
indeed synchrotron, the distinct spatial morphology and
very hard spectrum of the ICS are evidence that the electrons
responsible for the microwave and gamma-ray haze originate
from a harder source than supernova shocks. We describe
the full sky Fermi maps used in this analysis and make
them available for download.
| Title: |
Anomalous Expansion
of Attractively Interacting Fermionic Atoms in
an Optical Lattice |
| Authors: |
Hackermuller, Lucia; Schneider, Ulrich; Moreno-Cardoner, Maria; Kitagawa, Takuya; Will, Sebastian; Best, Thorsten; Demler, Eugene; Altman, Ehud; Bloch, Immanuel; Paredes, Belen |
| Publication: |
eprint arXiv:0910.3598 |
| Publication
Date: |
10/2009 |
| Origin: |
ARXIV |
| Keywords: |
Condensed Matter
- Quantum Gases, Condensed Matter - Strongly
Correlated Electrons |
| Comment: |
6 pages (plus appendix),
6 figures |
| Bibliographic
Code: |
2009arXiv0910.3598H |
Abstract
Strong correlations can dramatically modify the thermodynamics
of a quantum many-particle system. Especially intriguing
behaviour can appear when the system adiabatically enters
a strongly correlated regime, for the interplay between
entropy and strong interactions can lead to counterintuitive
effects. A well known example is the so-called Pomeranchuk
effect, occurring when liquid 3He is adiabatically compressed
towards its crystalline phase. Here, we report on a novel
anomalous, isentropic effect in a spin mixture of attractively
interacting fermionic atoms in an optical lattice. As
we adiabatically increase the attraction between the
atoms we observe that the gas, instead of contracting,
anomalously expands. This expansion results from the
combination of two effects induced by pair formation
in a lattice potential: the suppression of quantum fluctuations
as the attraction increases, which leads to a dominant
role of entropy, and the progressive loss of the spin
degree of freedom, which forces the gas to excite additional
orbital degrees of freedom and expand to outer regions
of the trap in order to maintain the entropy. The unexpected
thermodynamics we observe reveal fundamentally distinctive
features of pairing in the fermionic Hubbard model.
| Title: |
Novel Methods to
Create Multielectron Bubbles in Superfluid Helium |
| Authors: |
Fang, J.; Dementyev, Anatoly. E.; Tempere, J.; Silvera, Isaac F. |
| Publication: |
eprint arXiv:0910.3224 |
| Publication
Date: |
10/2009 |
| Origin: |
ARXIV |
| Keywords: |
Condensed Matter
- Other Condensed Matter, Condensed Matter -
Strongly Correlated Electrons |
| Comment: |
19 pages; 7 figures |
| Bibliographic
Code: |
2009arXiv0910.3224F |
Abstract
An equilibrium multielectron bubble in liquid helium
is a fascinating object with a spherical two-dimensional
electron gas on its surface. We describe two ways of
creating them. MEBs have been observed in the dome of
a cylindrical cell with an unexpectedly short lifetime;
we show analytically why these MEBs can discharge by
tunneling. Using a novel method, MEBs have been extracted
from a vapor sheath around a hot filament in superfluid
helium by applying electric fields up to 15 kV/cm, and
photographed with high-speed video. Charges as high as
1.6x10-9 C (~1010 electrons) have been measured. The
latter method provides a means of capture in an electromagnetic
trap to allow the study of the extensive exciting properties
of these elusive objects.
| Title: |
BPS Wall Crossing
and Topological Strings |
| Authors: |
Cecotti, Sergio; Vafa, Cumrun |
| Publication: |
eprint arXiv:0910.2615 |
| Publication
Date: |
10/2009 |
| Origin: |
ARXIV |
| Keywords: |
High Energy Physics
- Theory, Mathematics - Algebraic Geometry |
| Comment: |
18 pages |
| Bibliographic
Code: |
2009arXiv0910.2615C |
Abstract
By embedding N=2 gauge theories in string theory and
utilizing string dualities we map the counting of BPS
states with arbitrary electric and magnetic charges to
computations of an A-model topological string on an associated
geometry constructed from the data of the SW curve. We
show how the conjecture of Kontsevich and Soibelman regarding
wall crossing, as well as a more refined version which
captures the spin content of BPS states, is a natural
consequence. Chern-Simons theory realized on A-branes
and a twistorial construction play key roles.
Abstract
We study matter wave scattering from an ultracold, many
body atomic system trapped in an optical lattice. We
determine the angular cross section that a matter wave
probe sees and show that it is strongly affected by the
many body phase, superfluid or Mott insulator, of the
target lattice. We determine these cross sections analytically
in the first Born approximation, and we examine the variation
at intermediate points in the phase transition by numerically
diagonalizing the Bose Hubbard Hamiltonian for a small
lattice. We show that matter wave scattering offers a
convenient method for non-destructively probing the quantum
many body phase transition of atoms in an optical lattice.
| Title: |
Pi-phases in balanced
fermionic superfluids on spin-dependent optical
lattices |
| Authors: |
Zapata, I.; Wunsch, B.; Zinner, N. T.; Demler, E. |
| Publication: |
eprint arXiv:0910.1803 |
| Publication
Date: |
10/2009 |
| Origin: |
ARXIV |
| Keywords: |
Condensed Matter
- Quantum Gases, Condensed Matter - Mesoscale
and Nanoscale Physics, Condensed Matter - Strongly
Correlated Electrons |
| Comment: |
4 pages, 4 figures |
| Bibliographic
Code: |
2009arXiv0910.1803Z |
Abstract
We study a balanced two-component system of ultracold
fermions in one dimension with attractive interactions
and subject to a spin-dependent optical lattice potential
of opposite sign for the two components. The ground-state
develops a non-trivial superconducting order parameter
as the depth of the lattice is increased. The real-space
gap parameter changes sign and is analogous to the Fulde-Ferrell-Larkin-Ovchnnikov
states discussed in the context of superconductors in
magnetic fields. We discuss how to observe these $\pi$-phases
using the rapid-ramp technique. In addition we discuss
laser setups that can produce the required lattices needed
for these novel phases to appear.
| Title: |
Development of FTK
architecture: a fast hardware track trigger for
the ATLAS detector |
| Authors: |
Annovi, A.; Beretta, M.; Bossini, E.; Boveia, A.; Brubaker, E.; Canelli, F.; Cavasinni, V.; Crescioli, F.; DeBerg, H.; Dell'Orso, M.; Dunford, M.; Franklin, M.; Giannetti, P.; Kapliy, A.; Kim, Y. K.; Kimura, N.; Laurelli, P.; McCarn, A.; Melachrinos, C.; Mills, C.; Neubauer, M.; Proudfoot, J.; Piendibene, M.; Punzi, G.; Sarri, F.; Sartori, L.; Shochet, M.; Tripiccione, L.; Tuggle, J.; Vivarelli, I.; Volpi, G.; Yorita, K.; Zhang, J. |
| Publication: |
eprint arXiv:0910.1126 |
| Publication
Date: |
10/2009 |
| Origin: |
ARXIV |
| Keywords: |
Physics - Instrumentation
and Detectors, High Energy Physics - Experiment |
| Comment: |
To be published in
the proceedings of DPF-2009, Detroit, MI, July
2009, eConf C090726 |
| Bibliographic
Code: |
2009arXiv0910.1126A |
Abstract
The Fast Tracker (FTK) is a proposed upgrade to the ATLAS
trigger system that will operate at full Level-1 output
rates and provide high quality tracks reconstructed over
the entire detector by the start of processing in Level-2.
FTK solves the combinatorial challenge inherent to tracking
by exploiting the massive parallelism of Associative
Memories (AM) that can compare inner detector hits to
millions of pre-calculated patterns simultaneously. The
tracking problem within matched patterns is further simplified
by using pre-computed linearized fitting constants and
leveraging fast DSP's in modern commercial FPGA's. Overall,
FTK is able to compute the helix parameters for all tracks
in an event and apply quality cuts in approximately one
millisecond. By employing a pipelined architecture, FTK
is able to continuously operate at Level-1 rates without
deadtime. The system design is defined and studied using
ATLAS full simulation. Reconstruction quality is evaluated
for single muon events with zero pileup, as well as WH
events at the LHC design luminosity. FTK results are
compared with the tracking capability of an offline algorithm.
| Title: |
Heterogeneity and
Disorder: Contributions of Rolf Landauer |
| Authors: |
Halperin, Bertrand I.; Bergman, David J. |
| Publication: |
eprint arXiv:0910.0993 |
| Publication
Date: |
10/2009 |
| Origin: |
ARXIV |
| Keywords: |
Condensed Matter
- Materials Science, Condensed Matter - Disordered
Systems and Neural Networks, Condensed Matter
- Mesoscale and Nanoscale Physics, Physics -
History of Physics |
| Comment: |
10 pages, 3 figures;
presented on the occasion when Rolf Landauer
was awarded, posthumously, the inaugural ETOPIM
Medal at the ETOPIM 8 Conference, which took
place during 7--12 June, 2009 in Rethymnon, Crete |
| Bibliographic
Code: |
2009arXiv0910.0993H |
Abstract
Rolf Landauer made important contributions to many branches
of science. Within the broad area of transport in disordered
media, he wrote seminal papers on electrical conduction
in macroscopically inhomogeneous materials, as well as
fundamental analyses of electron transport in quantum
mechanical systems with disorder on the atomic scale.
We review here some of these contributions. We also briefly
describe some main events in his personal and scientific
life.
| Title: |
A statistical test
of emission from unresolved point sources |
| Authors: |
Slatyer, Tracy R.; Finkbeiner, Douglas P. |
| Publication: |
eprint arXiv:0910.0482 |
| Publication
Date: |
10/2009 |
| Origin: |
ARXIV |
| Keywords: |
Astrophysics - High
Energy Astrophysical Phenomena, Astrophysics
- Cosmology and Extragalactic Astrophysics, Astrophysics
- Instrumentation and Methods for Astrophysics |
| Comment: |
10 pages, 9 figures |
| Bibliographic
Code: |
2009arXiv0910.0482S |
Abstract
We describe a simple test of the spatial uniformity of
an ensemble of discrete events. Given an estimate for
the point source luminosity function and an instrumental
point spread function (PSF), a robust upper bound on
the fractional point source contribution to a diffuse
signal can be found. We verify with Monte Carlo tests
that the statistic is superior to the two-point correlation
function for this purpose, and derive analytic estimates
of the statistic's mean and variance as a function of
the point source contribution. As a case study, we apply
this statistic to recent gamma-ray data from the Fermi
Large Area Telescope (LAT), and demonstrate that at energies
above 10 GeV, the contribution of unresolved point sources
to the diffuse emission is small in the region relevant
for study of the WMAP Haze.
Abstract
We consider Yukawa couplings generated by a configuration
of intersecting seven-branes in F-theory. In configurations
with a single interaction point and no fluxes turned
on, the Yukawa matrices have rank one. This is no longer
true when the three-form H-flux is turned on, which is
generically the case for F-theory compactifications on
Calabi-Yau fourfolds. In the presence of H-fluxes, the
Yukawa coupling is computed using a non-commutative deformation
of holomorphic Chern-Simons theory (and its reduction
to seven-branes) and subsequently the rank of the Yukawa
matrix changes. Such fluxes give rise to a hierarchical
structure in the Yukawa matrix in F-theory GUTs of the
type which has recently been proposed as a resolution
of the flavor hierarchy problem.
| Title: |
Optical Cross Correlation
Filters: An Economical Approach for Identifying
SNe Ia and Estimating their Redshifts |
| Authors: |
Scolnic, D. M.; Riess, A. G.; Huber, M. E.; Rest, A.; Stubbs, C.; Tonry, J. L. |
| Publication: |
eprint arXiv:0910.0075 |
| Publication
Date: |
10/2009 |
| Origin: |
ARXIV |
| Keywords: |
Astrophysics - Instrumentation
and Methods for Astrophysics, Astrophysics -
Cosmology and Extragalactic Astrophysics |
| Comment: |
Accepted for The
Astrophysical Journal. 30 pages, 19 figures |
| Bibliographic
Code: |
2009arXiv0910.0075S |
Abstract
Large photometric surveys of transient phenomena, such
as Pan-STARRS and LSST, will locate thousands to millions
of type Ia supernova candidates per year, a rate prohibitive
for acquiring spectroscopy to determine each candidate's
type and redshift. In response, we have developed an
economical approach to identifying SNe Ia and their redshifts
using an uncommon type of optical filter which has multiple,
discontinuous passbands on a single substrate. Observation
of a supernova through a specially designed pair of these
`cross-correlation filters' measures the approximate
amplitude and phase of the cross-correlation between
the spectrum and a SN Ia template, a quantity typically
used to determine the redshift and type of a high-redshift
SN Ia. Simulating the use of these filters, we obtain
a sample of SNe Ia which is ~98% pure with individual
redshifts measured to 0.01 precision. The advantages
of this approach over standard broadband photometric
methods are that it is insensitive to reddening, independent
of the color data used for subsequent distance determinations
which reduces selection or interpretation bias, and because
it makes use of the spectral features its reliability
is greater. A great advantage over long-slit spectroscopy
comes from increased throughput, enhanced multiplexing
and reduced set-up time resulting in a net gain in speed
of up to ~30 times. This approach is also insensitive
to host galaxy contamination. Prototype filters were
built and successfully used on Magellan with LDSS-3 to
characterize three SNLS candidates. We discuss how these
filters can provide critical information for the upcoming
photometric supernova surveys.
| Title: |
A decade of SN 1993J:
discovery of radio wavelength effects in the
expansion rate |
| Authors: |
Marcaide, J. M.; Martí-Vidal, I.; Alberdi, A.; Pérez-Torres, M. A.; Ros, E.; Diamond, P. J.; Guirado, J. C.; Lara, L.; Shapiro, I. I.; Stockdale, C. J.; Weiler, K. W.; Mantovani, F.; Preston, R. A.; Schilizzi, R. T.; Sramek, R. A.; Trigilio, C.; van Dyk, S. D.; Whitney, A. R. |
| Publication: |
Astronomy and Astrophysics,
Volume 505, Issue 3, 2009, pp.927-945 (A&A
Homepage) |
| Publication
Date: |
10/2009 |
| Origin: |
EDP
Sciences |
| Keywords: |
galaxies: clusters:
individual: M 81, radio continuum: stars, supernovae:
general, supernovae: individual: SN 1993J, techniques:
interferometric |
| DOI: |
10.1051/0004-6361/200912133 |
| Bibliographic
Code: |
2009A&A...505..927M |
Abstract
We studied the growth of the shell-like radio structure
of supernova SN 1993J in M 81 from September 1993 to
October 2003 with very-long-baseline interferometry (VLBI)
observations at the wavelengths of 3.6, 6, and 18 cm.
We developed a method to accurately determine the outer
radius (R) of any circularly symmetric compact radio
structure such as SN 1993J. The source structure of SN
1993J remains circularly symmetric (with deviations from
circularity under 2%) over almost 4000 days. We characterize
the decelerated expansion of SN 1993J until approximately
day 1500 after explosion with an expansion parameter
m = 0.845±0.005 (R ∝ tm). However, from that day onwards
the expansion differs when observed at 6 and 18 cm. Indeed,
at 18 cm, the expansion can be well characterized by
the same m as before day 1500, while at 6 cm the expansion
appears more decelerated, and is characterized by another
expansion parameter, m6 = 0.788±0.015. Therefore, since
about day 1500 onwards, the radio source size has been
progressively smaller at 6 cm than at 18 cm. These findings
differ significantly from those of other authors in the
details of the expansion. In our interpretation, the
supernova expands with a single expansion parameter,
m = 0.845±0.005, and the 6 cm results beyond day 1500
are caused by physical effects, perhaps also coupled
to instrumental limitations. Two physical effects may
be involved: (a) a changing opacity of the ejecta to
the 6 cm radiation; and (b) a radial decrease of the
magnetic field in the emitting region. We also found
that at 6 cm about 80% of the radio emission from the
backside of the shell behind the ejecta is absorbed (our
average estimate, since we cannot determine any possible
evolution of the opacity), and the width of the radio
shell is (31±2)% of the outer radius. The shell width
at 18 cm depends on the degree of assumed absorption.
For 80% absorption, the width is (33.5±1.7)%, and for
100% absorption, it is (37.8±1.3)%. A comparison of our
VLBI results with optical spectral line velocities shows
that the deceleration is more pronounced in the radio
than in the optical. This difference might be due to
a progressive penetration of ejecta instabilities into
the shocked circumstellar medium, as also suggested by
other authors.
| see
also: |
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Oct., 2007 |
Nov., 2007 |
Dec., 2007 |
| Jan., 2008 |
Feb., 2008 |
Mar., 2008 |
Apr., 2008 |
May, 2008 |
June, 2008 |
| July, 2008 |
Aug., 2008 |
Sep., 2008 |
Oct., 2008 |
Nov., 2008 |
Dec., 2008 |
| Jan., 2009 |
Feb., 2009 |
Mar., 2009 |
Apr., 2009 |
May, 2009 |
June, 2009 |
| July, 2009 |
Aug., 2009 |
Sep., 2009 |
|
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