95 research outputs found
Are serial CA 19-9 kinetics helpful in predicting survival in patients with advanced or metastatic pancreatic cancer treated with gemcitabine and cisplatin?
Background: Serial kinetics of serum CA 19-9 levels have been reported to reflect response and survival in patients with pancreatic cancer undergoing surgery, radiotherapy, and chemotherapy. We prospectively studied serial kinetics of serum CA 19-9 levels of patients with locally advanced or metastatic disease treated with gemcitabine and cisplatin. Patients and Methods: Enrolled in the study were 87 patients (female/male = 26/61; stage III/IV disease = 24/63). Patients received gemcitabine 1,000 mg/m(2) on days 1, 8, and 15 plus cisplatin 50 mg/m(2) on days 1 and 15, every 4 weeks. Serum samples were collected at the onset of chemotherapy and before the start of a new treatment cycle (day 28). Results: 77 of 87 patients (88.5%) with initially elevated CA 19-9 levels were included for evaluation. According to imaging criteria, 4 (5.2%) achieved a complete remission and 11 (14.3%) achieved partial remission, yielding an overall response rate of 19.5%. 43 (55.8%) patients were CA 19-9 responders, defined by greater than or equal to50% decrease in CA 19-9 serum levels within 2 months after treatment initiation. Except for one, all patients who had responded by imaging criteria (n = 14) fulfilled the criterion of a CA 19-9 responder. Despite being characterized as non-responders by CT-imaging criteria (stable/progressive disease), 29 patients were classified as CA 19-9 responders (positive predictive value 32.5%). Independent of the response evaluation by CT, CA 19-9 responders survived significantly longer than CA 19-9 non-responders (295 d; 95% CI: 285-445 vs. 174 d; 95% CI: 134-198; p = 0.022). Conclusion: CA 19-9 kinetics in serum serve as an early and reliable indicator of response and help to predict survival in patients with advanced pancreatic cancer receiving effective treatment with gemcitabine and cisplatin
Unruh response functions for scalar fields in de Sitter space
We calculate the response functions of a freely falling Unruh detector in de
Sitter space coupled to scalar fields of different coupling to the curvature,
including the minimally coupled massless case. Although the responses differ
strongly in the infrared as a consequence of the amplification of superhorizon
modes, the energy levels of the detector are thermally populated.Comment: 16 pages, 1 figure, accepted for publication by Classical and Quantum
Gravit
Right-handed Sneutrinos as Nonthermal Dark Matter
When the minimal supersymmetric standard model is augmented by three
right-handed neutrino superfields, one generically predicts that the neutrinos
acquire Majorana masses. We postulate that all supersymmetry (SUSY) breaking
masses as well as the Majorana masses of the right-handed neutrinos are around
the electroweak scale and, motivated by the smallness of neutrino masses,
assume that the lightest supersymmetric particle (LSP) is an almost-pure
right-handed sneutrino. We discuss the conditions under which this LSP is a
successful dark matter candidate. In general, such an LSP has to be nonthermal
in order not to overclose the universe, and we find the conditions under which
this is indeed the case by comparing the Hubble expansion rate with the rates
of the relevant thermalizing processes, including self-annihilation and
co-annihilation with other SUSY and standard model particles.Comment: 17 pages v.2: References adde
Hybrid inflation followed by modular inflation
Inflationary models with a superheavy scale F-term hybrid inflation followed
by an intermediate scale modular inflation are considered. The restrictions on
the power spectrum P_R of curvature perturbation and the spectral index n_s
from the recent data within the power-law cosmological model with cold dark
matter and a cosmological constant can be met provided that the number of
e-foldings N_HI* suffered by the pivot scale k_*=0.002/Mpc during hybrid
inflation is suitably restricted. The additional e-foldings needed for solving
the horizon and flatness problems are generated by modular inflation with a
string axion as inflaton. For central values of P_R and n_s, the grand
unification scale comes out, in the case of standard hybrid inflation, close to
its supersymmetric value M_GUT=2.86 x 10^16 GeV, the relevant coupling constant
is relatively large (0.005-0.14), and N_HI* is between 10 and 21.7. In the
shifted [smooth] hybrid inflation case, the grand unification scale can be
identified with M_GUT for N_HI*=21 [N_HI*=18].Comment: 13 pages including 3 figures, uses ws-ijmpa.cls, minor corrections
included, talk given at the CTP Symposium on Supersymmetry at LHC:
Theoretical and Experimental Perspectives, British University in Egypt (BUE),
Cairo, 11-14 March 2007 (to appear in the proceedings
Resonant decay of flat directions
We study preheating, i.e., non-perturbative resonant decay, of flat direction
fields, concentrating on MSSM flat directions and the right handed sneutrino.
The difference between inflaton preheating and flaton preheating, is that the
potential is more constraint in the latter case. The effects of a complex
driving field, quartic couplings in the potential, and the presence of a
thermal bath are important and cannot be neglected.
Preheating of MSSM flat directions is typically delayed due to out-of-phase
oscillations of the real and imaginary components and may be preceded by
perturbative decay or -ball formation. Particle production due to the
violation of adiabaticity is expected to be inefficient due to back reaction
effects. For a small initial sneutrino VEV, with
the mass of the right handed sneutrino and a yakawa coupling, there are
tachyonic instabilities. The -term quartic couplings do not generate an
effective mass for the tachyonic modes, making it an efficient decay channel.
It is unclear how thermal scattering affects the resonance.Comment: 20 pages, 4 figure
Flavour-coherent propagators and Feynman rules: Covariant cQPA formulation
We present a simplified and generalized derivation of the flavour-coherent
propagators and Feynman rules for the fermionic kinetic theory based on
coherent quasiparticle approximation (cQPA). The new formulation immediately
reveals the composite nature of the cQPA Wightman function as a product of two
spectral functions and an effective two-point interaction vertex, which
contains all quantum statistical and coherence information. We extend our
previous work to the case of nonzero dispersive self-energy, which leads to a
broader range of applications. By this scheme, we derive flavoured kinetic
equations for local 2-point functions , which are
reminiscent of the equations of motion for the density matrix. We emphasize
that in our approach all the interaction terms are derived from first
principles of nonequilibrium quantum field theory.Comment: 20 pages, 3 figures. Minor modifications, version published in JHE
Probing leptogenesis
The focus of this paper lies on the possible experimental tests of leptogenesis scenarios. We consider both leptogenesis generated from oscillations, as well as leptogenesis from out-of-equilibrium decays. As the Akhmedov-Rubakov-Smirnov (ARS) mechanism allows for heavy neutrinos in the GeV range, this opens up a plethora of possible experimental tests, e.g. at neutrino oscillation experiments, neutrinoless double beta decay, and direct searches for neutral heavy leptons at future facilities. In contrast, testing leptogenesis from out-of-equilibrium decays is a quite difficult task. We comment on the necessary conditions for having successful leptogenesis at the TeV-scale. We further discuss possible realizations and their model specific testability in extended seesaw models, models with extended gauge sectors, and supersymmetric leptogenesis. Not being able to test high-scale leptogenesis directly, we present a way to falsify such scenarios by focusing on their washout processes. This is discussed specifically for the left-right symmetric model and the observation of a heavy WR, as well as model independently when measuring L = 2 washout processes at the LHC or neutrinoless double beta decay.Fil: Chun, E. J.. Korea Institute For Advanced Study; Corea del SurFil: Cvetic, G.. Universidad Técnica Federico Santa María; ChileFil: Dev, P. S. B.. Washington University in St. Louis; Estados UnidosFil: Drewes, Alejandro Marcelo. Technische Universitat München; Alemania. Université Catholique de Louvain; BélgicaFil: Fong, C. S.. Universidade de Sao Paulo; BrasilFil: Garbrecht, B.. Technische Universitat München; AlemaniaFil: Hambye, T.. Université Libre de Bruxelles; BélgicaFil: Harz, J.. Institut Lagrange de Paris, Sorbonne Universitès; Francia. Centre National de la Recherche Scientifique; FranciaFil: Hernández, P.. Cern - European Organization For Nuclear Research; Suiza. Universidad de Valencia; EspañaFil: Kim, C. S.. Department Of Physics And Ipap, Yonsei University; Corea del SurFil: Molinaro, E.. University Of Southern Denmark; DinamarcaFil: Nardi, E.. Laboratori Nazionali Di Frascati; ItaliaFil: Racker, Juan Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Rius, N.. Universidad de Valencia; EspañaFil: Zamora-Saa, J.. Joint Institute For Nuclear Research; Rusi
Constraints on Brane Inflation and Cosmic Strings
By considering simple, but representative, models of brane inflation from a
single brane-antibrane pair in the slow roll regime, we provide constraints on
the parameters of the theory imposed by measurements of the CMB anisotropies by
WMAP including a cosmic string component. We find that inclusion of the string
component is critical in constraining parameters. In the most general model
studied, which includes an inflaton mass term, as well as the brane-antibrane
attraction, values n_s < 1.02 are compatible with the data at 95 % confidence
level. We are also able to constrain the volume of internal manifold (modulo
factors dependent on the warp factor) and the value of the inflaton field to be
less than 0.66M_P at horizon exit. We also investigate models with a mass term.
These observational considerations suggest that such models have r < 2*10^-5,
which can only be circumvented in the fast roll regime, or by increasing the
number of antibranes. Such a value of r would not be detectable in CMB
polarization experiment likely in the near future, but the B-mode signal from
the cosmic strings could be detectable. We present forecasts of what a similar
analysis using PLANCK data would yield and find that it should be possible to
rule out G\mu > 6.5*10^-8 using just the TT, TE and EE power spectra.Comment: 11 pages, 3 figures, revtex4, typos corrected, references adde
Thermal production of relativistic Majorana neutrinos: Strong enhancement by multiple soft scattering
The production rate of heavy Majorana neutrinos is relevant for models of
thermal leptogenesis in the early Universe. In the high temperature limit the
production can proceed via the 1 2 (inverse) decays which are allowed by
the thermal masses. We consider new production mechanisms which are obtained by
including additional soft gauge interactions with the plasma. We show that an
arbitrary number of such interactions gives leading order contributions, and we
sum all of them. The rate turns out to be smooth in the region where the 1
2 processes are kinematically forbidden. At higher temperature it is enhanced
by a factor 3 compared to the 1 2 rate.Comment: 26 pages, 8 figures; added references, added comments on 2 to 2
scattering processes, improved appearance of fig. 8, corrected typos; matches
published versio
The Minimal Scale Invariant Extension of the Standard Model
We perform a systematic analysis of an extension of the Standard Model that
includes a complex singlet scalar field and is scale invariant at the tree
level. We call such a model the Minimal Scale Invariant extension of the
Standard Model (MSISM). The tree-level scale invariance of the model is
explicitly broken by quantum corrections, which can trigger electroweak
symmetry breaking and potentially provide a mechanism for solving the gauge
hierarchy problem. Even though the scale invariant Standard Model is not a
realistic scenario, the addition of a complex singlet scalar field may result
in a perturbative and phenomenologically viable theory. We present a complete
classification of the flat directions which may occur in the classical scalar
potential of the MSISM. After calculating the one-loop effective potential of
the MSISM, we investigate a number of representative scenarios and determine
their scalar boson mass spectra, as well as their perturbatively allowed
parameter space compatible with electroweak precision data. We discuss the
phenomenological implications of these scenarios, in particular, whether they
realize explicit or spontaneous CP violation, neutrino masses or provide dark
matter candidates. In particular, we find a new minimal scale-invariant model
of maximal spontaneous CP violation which can stay perturbative up to
Planck-mass energy scales, without introducing an unnaturally large hierarchy
in the scalar-potential couplings.Comment: 71 pages, 34 eps figures, numerical error corrected, clarifying
comments adde
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