1,821 research outputs found
Quantum limit of deterministic theories
We show that the quantum linear harmonic oscillator can be obtained in the
large limit of a classical deterministic system with SU(1,1) dynamical
symmetry. This is done in analogy with recent work by G.'t Hooft who
investigated a deterministic system based on SU(2). Among the advantages of our
model based on a non--compact group is the fact that the ground state energy is
uniquely fixed by the choice of the representation.Comment: 4 pages, 2 figures, minor corrections added. To appear in the
Proceedings of Waseda International Symposium on Fundamental Physics: "New
Perspectives in Quantum Physics", 12-15 November 2002, Waseda University,
Tokyo, Japa
Comments on large-N volume independence
We study aspects of the large-N volume independence on R**3 x L**G, where
L**G is a G-site lattice for Yang-Mills theory with adjoint Wilson-fermions. We
find the critical number of lattice sites above which the center-symmetry
analysis on L**G agrees with the one on the continuum S**1. For Wilson
parameter set to one and G>=2, the two analyses agree. One-loop radiative
corrections to Wilson-line masses are finite, reminiscent of the
UV-insensitivity of the Higgs mass in deconstruction/Little-Higgs theories.
Even for theories with G=1, volume independence in QCD(adj) may be guaranteed
to work by tuning one low-energy effective field theory parameter. Within the
parameter space of the theory, at most three operators of the 3d effective
field theory exhibit one-loop UV-sensitivity. This opens the analytical
prospect to study 4d non-perturbative physics by using lower dimensional field
theories (d=3, in our example).Comment: 12 pages; added small clarifications, published versio
Lipid Peroxidation and Depressed Mood in Community-Dwelling Older Men and Women
It has been hypothesized that cellular damage caused by oxidative stress is associated with late-life depression but\ud
epidemiological evidence is limited. In the present study we evaluated the association between urinary 8-iso-prostaglandin\ud
F2a (8-iso-PGF2a), a biomarker of lipid peroxidation, and depressed mood in a large sample of community-dwelling older\ud
adults. Participants were selected from the Health, Aging and Body Composition study, a community-based longitudinal\ud
study of older persons (aged 70â79 years). The present analyses was based on a subsample of 1027 men and 948 women\ud
free of mobility disability. Urinary concentration of 8-iso-PGF2a was measured by radioimmunoassay methods and adjusted\ud
for urinary creatinine. Depressed mood was defined as a score greater than 5 on the 15-item Geriatric Depression Scale and/\ud
or use of antidepressant medications. Depressed mood was present in 3.0% of men and 5.5% of women. Depressed men\ud
presented higher urinary concentrations of 8-iso-PGF2a than non-depressed men even after adjustment for multiple\ud
sociodemographic, lifestyle and health factors (p=0.03, Cohenâs d = 0.30). This association was not present in women\ud
(depressed status-by-sex interaction p = 0.04). Our study showed that oxidative damage may be linked to depression in\ud
older men from a large sample of the general population. Further studies are needed to explore whether the modulation of\ud
oxidative stress may break down the link between late-life depression and its deleterious health consequences
A Reversible Gene-Targeting Strategy Identifies Synthetic Lethal Interactions between MK2 and p53 in the DNA Damage Response In Vivo
A fundamental limitation in devising new therapeutic strategies for killing cancer cells with DNA damaging agents is the need to identify synthetic lethal interactions between tumor-specific mutations and components of the DNA damage response (DDR) in vivo. The stress-activated p38 mitogen-activated protein kinase (MAPK)/MAPKAP kinase-2 (MK2) pathway is a critical component of the DDR network in p53-deficient tumor cells in vitro. To explore the relevance of this pathway for cancer therapy in vivo, we developed a specific gene targeting strategy in which Cre-mediated recombination simultaneously creates isogenic MK2-proficient and MK2-deficient tumors within a single animal. This allows direct identification of MK2 synthetic lethality with mutations that promote tumor development or control response to genotoxic treatment. In an autochthonous model of non-small-cell lung cancer (NSCLC), we demonstrate that MK2 is responsible for resistance of p53-deficient tumors to cisplatin, indicating synthetic lethality between p53 and MK2 can successfully be exploited for enhanced sensitization of tumors to DNA-damaging chemotherapeutics in vivo.National Institutes of Health (U.S.) (Grant ES015339)National Institutes of Health (U.S.) (Grant GM60594)National Institutes of Health (U.S.) (Grant GM59281)National Institutes of Health (U.S.) (Grant CA112967)Janssen Pharmaceutical Ltd.Massachusetts Institute of Technology. Center for Environmental Health Sciences (Core Grant P30-CA14051)Massachusetts Institute of Technology. Center for Environmental Health Sciences (Core Grant ES-002109
GASP XXIV. The history of abruptly quenched galaxies in clusters
The study of cluster post starburst galaxies gives useful insights on the
physical processes quenching the star formation in the most massive
environments. Exploiting the MUSE data of the GAs Stripping Phenomena in
galaxies (GASP) project, we characterise the quenching history of 8 local
cluster galaxies that were selected for not showing emission lines in their
fiber spectra. We inspect the integrated colors, the Hb rest frame equivalent
widths (EW), star formation histories (SFHs) and luminosity-weighted age (LWA)
maps finding no signs of current star formation throughout the disks of these
early-spiral/S0 galaxies. All of them have been passive for at least 20 Myr,
but their SF declined on different timescales. In most of them the outskirts
reached undetectable SFRs before the inner regions (outside-in quenching). Our
sample includes three post-starforming galaxies, two passive galaxies and three
galaxies with intermediate properties. The first population shows blue colors,
deep Hb in absorption (EW>>2.8A), young ages (8.8<log(LW [yr])<9.2). Two of
these galaxies show signs of a central SF enhancement before quenching. Passive
galaxies have instead red colors, EW(Hb)<2.8A, ages in the range
9.2<log(LWA[yr])<10. Finally, the other galaxies are most likely in transition
between a post starforming and passive phase, as they quenched in an
intermediate epoch and have not lost all the star forming features yet. The
outside-in quenching, the morphology and kinematics of the stellar component,
along with the position of these galaxies within massive clusters
(sigma_cl=550-950km/s) point to a scenario in which ram pressure stripping has
removed the gas, leading to quenching. Only the three most massive galaxies
might alternatively have entered the clusters already quenched. These galaxies
are therefore at the final stage of the rapid evolution galaxies undergo when
they enter the clusters.Comment: 24 pages, 10 figures accepted for publication in Ap
Effective lattice theories for Polyakov loops
We derive effective actions for SU(2) Polyakov loops using inverse Monte
Carlo techniques. In a first approach, we determine the effective couplings by
requiring that the effective ensemble reproduces the single-site distribution
of the Polyakov loops. The latter is flat below the critical temperature
implying that the (untraced) Polyakov loop is distributed uniformly over its
target space, the SU(2) group manifold. This allows for an analytic
determination of the Binder cumulant and the distribution of the mean-field,
which turns out to be approximately Gaussian. In a second approach, we employ
novel lattice Schwinger-Dyson equations which reflect the SU(2) x SU(2)
invariance of the functional Haar measure. Expanding the effective action in
terms of SU(2) group characters makes the numerics sufficiently stable so that
we are able to extract a total number of 14 couplings. The resulting action is
short-ranged and reproduces the Yang-Mills correlators very well.Comment: 27 pages, 8 figures, v2: method refined, chapter and references adde
Effective Kinetic Theory for High Temperature Gauge Theories
Quasiparticle dynamics in relativistic plasmas associated with hot,
weakly-coupled gauge theories (such as QCD at asymptotically high temperature
) can be described by an effective kinetic theory, valid on sufficiently
large time and distance scales. The appropriate Boltzmann equations depend on
effective scattering rates for various types of collisions that can occur in
the plasma. The resulting effective kinetic theory may be used to evaluate
observables which are dominantly sensitive to the dynamics of typical
ultrarelativistic excitations. This includes transport coefficients
(viscosities and diffusion constants) and energy loss rates. We show how to
formulate effective Boltzmann equations which will be adequate to compute such
observables to leading order in the running coupling of high-temperature
gauge theories [and all orders in ]. As previously proposed
in the literature, a leading-order treatment requires including both
particle scattering processes as well as effective ``'' collinear
splitting processes in the Boltzmann equations. The latter account for nearly
collinear bremsstrahlung and pair production/annihilation processes which take
place in the presence of fluctuations in the background gauge field. Our
effective kinetic theory is applicable not only to near-equilibrium systems
(relevant for the calculation of transport coefficients), but also to highly
non-equilibrium situations, provided some simple conditions on distribution
functions are satisfied.Comment: 40 pages, new subsection on soft gauge field instabilities adde
An integrated comparative phosphoproteomic and bioinformatic approach reveals a novel class of MPM-2 motifs upregulated in EGFRvIII-expressing Glioblastoma Cells
Glioblastoma (GBM, WHO grade IV) is an aggressively proliferative and invasive brain tumor that carries a poor clinical prognosis with a median survival of 9 to 12 months. In a prior phosphoproteomic study performed in the U87MG glioblastoma cell line, we identified tyrosine phosphorylation events that are regulated as a result of titrating EGFRvIII, a constitutively active mutant of the epidermal growth factor receptor (EGFR) associated with poor prognosis in GBM patients. In the present study, we have used the phosphoserine/phosphothreonine-specific antibody MPM-2 (mitotic protein monoclonal #2) to quantify serine/threonine phosphorylation events in the same cell lines. By employing a bioinformatic tool to identify amino acid sequence motifs regulated in response to increasing oncogene levels, a set of previously undescribed MPM-2 epitope sequence motifs orthogonal to the canonical âpS/pT-Pâ motif was identified. These motifs contain acidic amino acids in combinations of the â5, â2, +1, +3, and +5 positions relative to the phosphorylated amino acid. Phosphopeptides containing these motifs are upregulated in cells expressing EGFRvIII, raising the possibility of a general role for a previously unrecognized acidophilic kinase (e.g. casein kinase II (CK2)) in cell proliferation downstream of EGFR signaling.National Cancer Institute (U.S.). Integrative Cancer Biology Program (grant U54-CA112967)National Cancer Institute (U.S.). Bioengineering Research Partnership (grant R01-CA96504)National Institutes of Health (U.S.) (grant R01-GM60594
Exponentiation of Multiparticle Amplitudes in Scalar Theories
It is argued that the amplitudes of the production of soft scalar
particles by one or a few energetic ones in theories like has
the exponential form, , in the regime , ,
, where is the typical kinetic energy of outgoing
particles. Existing results support this conjecture. Several new analytical and
numerical results in favor of the exponential behavior of multiparticle
amplitudes are presented.Comment: Revtex 3.0, 45 pages, 11 figures (some requires bezier.sty, two
postscript figures appended after \end{document}), INR-866/9
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