329 research outputs found
New Physics and the Landau Pole
In scalar field theories the Landau pole is an ultraviolet singularity in the
running coupling constant that indicates a mass scale at which the theory
breaks down and new physics must intervene. However, new physics at the pole
will in general affect the running of the low energy coupling constant, which
will in turn affect the location of the pole and the related upper limit
(``triviality'' bound) on the low energy coupling constant. If the new physics
is strongly coupled to the scalar fields these effects can be significant even
though they are power suppressed. We explore the possible range of such effects
by deriving the one loop renormalization group equations for an effective
scalar field theory with a dimension 6 operator representing the low energy
effects of the new physics. As an independent check we also consider a
renormalizable model of the high-scale physics constructed so that its low
energy limit coincides with the effective theory.Comment: 26 pages, 5 figure
Effects of technicolor on standard model running couplings
We discuss the running couplings in the standard model, SU(3SU(2U(1, when the Higgs sector is replaced by SU(
technicolor. Particular attention is given to the running of the couplings at
momentum scales where technicolor is nonperturbative, and in this region we
apply a relativistic constituent technifermion model. This model has been
tested against the known running of the QED coupling due to nonperturbative
QCD. An understanding of this low momentum running allows the calculation of
the couplings at a higher scale, , where technicolor becomes
perturbative. We provide numerical values for the changes in the three standard
model couplings between and due to technicolor, assuming
separately ``one doublet'' and ``one family'' technicolor models. The
distinction between a running and walking technicolor coupling is also
considered.Comment: 14 pages of LaTeX, UTPT-94-
Exact steady-state velocity of ratchets driven by random sequential adsorption
We solve the problem of discrete translocation of a polymer through a pore,
driven by the irreversible, random sequential adsorption of particles on one
side of the pore. Although the kinetics of the wall motion and the deposition
are coupled, we find the exact steady-state distribution for the gap between
the wall and the nearest deposited particle. This result enables us to
construct the mean translocation velocity demonstrating that translocation is
faster when the adsorbing particles are smaller. Monte-Carlo simulations also
show that smaller particles gives less dispersion in the ratcheted motion. We
also define and compare the relative efficiencies of ratcheting by deposition
of particles with different sizes and we describe an associated
"zone-refinement" process.Comment: 11 pages, 4 figures New asymptotic result for low chaperone density
added. Exact translocation velocity is proportional to (chaperone
density)^(1/3
One loop corrections to quantum hadrodynamics with vector mesons
The renormalized elastic scattering amplitude to one loop is
calculated in the chiral limit in the model and in a Quantum
Hadrodynamic model (QHD-III) with vector mesons. It is argued that QHD-III
reduces to the linear model in the limit that the vector meson masses
become large. The pion decay constant is also calculated to 1-loop in the
model, and at tree level in QHD-III; it is shown that the coefficient
of the tree level term in the scattering amplitude equals . The
1-loop correction of in QHD-III violates strong isospin current
conservation. Thus,it is concluded that QHD-III can, at best, only describe the
strongly interacting nuclear sector.Comment: 6 page
Information metric from a linear sigma model
The idea that a spacetime metric emerges as a Fisher-Rao `information metric'
of instanton moduli space has been examined in several field theories such as
the Yang-Mills theories and nonlinear sigma models. In this brief paper, we
report that the flat Euclidean or Minkowskian metric, rather than an anti-de
Sitter metric that generically emerges from instanton moduli spaces, can be
obtained as the Fisher-Rao metric from a non-trivial solution of the massive
Klein-Gordon field (a linear sigma model). This realization of the flat space
from the simple field theory would be useful to investigate the ideas that
relate the spacetime geometry with the information geometry.Comment: 8 pages, 1 figure, to appear in PR
Relative entropy, Haar measures and relativistic canonical velocity distributions
The thermodynamic maximum principle for the Boltzmann-Gibbs-Shannon (BGS)
entropy is reconsidered by combining elements from group and measure theory.
Our analysis starts by noting that the BGS entropy is a special case of
relative entropy. The latter characterizes probability distributions with
respect to a pre-specified reference measure. To identify the canonical BGS
entropy with a relative entropy is appealing for two reasons: (i) the maximum
entropy principle assumes a coordinate invariant form; (ii) thermodynamic
equilibrium distributions, which are obtained as solutions of the maximum
entropy problem, may be characterized in terms of the transformation properties
of the underlying reference measure (e.g., invariance under group
transformations). As examples, we analyze two frequently considered candidates
for the one-particle equilibrium velocity distribution of an ideal gas of
relativistic particles. It becomes evident that the standard J\"uttner
distribution is related to the (additive) translation group on momentum space.
Alternatively, imposing Lorentz invariance of the reference measure leads to a
so-called modified J\"uttner function, which differs from the standard
J\"uttner distribution by a prefactor, proportional to the inverse particle
energy.Comment: 15 pages: extended version, references adde
Hydrogen atom in phase space: The Wigner representation
We have found an effective method of calculating the Wigner function, being a
quantum analogue of joint probability distribution of position and momentum,
for bound states of nonrelativistic hydrogen atom. The formal similarity
between the eigenfunctions of nonrelativistic hydrogen atom in the momentum
representation and Klein-Gordon propagators has allowed the calculation of the
Wigner function for an arbitrary bound state of the hydrogen atom. These Wigner
functions for some low lying states are depicted and discussed.Comment: 8 pages (including figures
Dynamics of open quantum systems
The coupling between the states of a system and the continuum into which it
is embedded, induces correlations that are especially large in the short time
scale. These correlations cannot be calculated by using a statistical or
perturbational approach. They are, however, involved in an approach describing
structure and reaction aspects in a unified manner. Such a model is the SMEC
(shell model embedded in the continuum). Some characteristic results obtained
from SMEC as well as some aspects of the correlations induced by the coupling
to the continuum are discussed.Comment: 16 pages, 5 figure
Hitting sbottom in natural SUSY
We compare the experimental prospects of direct stop and sbottom pair
production searches at the LHC. Such searches for stops are of great interest
as they directly probe for states that are motivated by the SUSY solution to
the hierarchy problem of the Higgs mass parameter - leading to a "Natural" SUSY
spectrum. Noting that sbottom searches are less experimentally challenging and
scale up in reach directly with the improvement on b-tagging algorithms, we
discuss the interplay of small TeV scale custodial symmetry violation with
sbottom direct pair production searches as a path to obtaining strong sub-TeV
constraints on stops in a natural SUSY scenario. We argue that if a weak scale
natural SUSY spectrum does not exist within the reach of LHC, then hopes for
such a spectrum for large regions of parameter space should sbottom out.
Conversely, the same arguments make clear that a discovery of such a spectrum
is likely to proceed in a sbottom up manner.Comment: 18 pages, 8 figures,v2 refs added, JHEP versio
On the Long-Range Exciton Transport in Molecular Systems: The Application to H-Aggregated Heterotriangulene Chains
© 2017 American Chemical Society. Self-assembled aggregates of pigment molecules are potential building blocks for excitonic circuits that find their application in energy conversion and optical signal processing. Recent experimental studies of one-dimensional heterotriangulene supramolecular aggregates suggested that singlet excitons in these structures can propagate on several micron distances. We explore this possibility theoretically by combining electronic structure calculations with microscopic models for exciton transport. A detailed characterization of the structural disorder and exciton decoherence is provided. We argue that advanced, well-established exciton transport models, used in our study, give about one order of magnitude shorter estimates for the exciton propagation length which suggest that there are other possible explanations of the experimental results
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