693 research outputs found
Lorentz violating kinematics: Threshold theorems
Recent tentative experimental indications, and the subsequent theoretical
speculations, regarding possible violations of Lorentz invariance have
attracted a vast amount of attention. An important technical issue that
considerably complicates detailed calculations in any such scenario, is that
once one violates Lorentz invariance the analysis of thresholds in both
scattering and decay processes becomes extremely subtle, with many new and
naively unexpected effects. In the current article we develop several extremely
general threshold theorems that depend only on the existence of some energy
momentum relation E(p), eschewing even assumptions of isotropy or monotonicity.
We shall argue that there are physically interesting situations where such a
level of generality is called for, and that existing (partial) results in the
literature make unnecessary technical assumptions. Even in this most general of
settings, we show that at threshold all final state particles move with the
same 3-velocity, while initial state particles must have 3-velocities
parallel/anti-parallel to the final state particles. In contrast the various
3-momenta can behave in a complicated and counter-intuitive manner.Comment: V1: 32 pages, 6 figures, 3 tables. V2: 5 references adde
Renormalizable acausal theories of classical gravity coupled with interacting quantum fields
We prove the renormalizability of various theories of classical gravity
coupled with interacting quantum fields. The models contain vertices with
dimensionality greater than four, a finite number of matter operators and a
finite or reduced number of independent couplings. An interesting class of
models is obtained from ordinary power-counting renormalizable theories,
letting the couplings depend on the scalar curvature R of spacetime. The
divergences are removed without introducing higher-derivative kinetic terms in
the gravitational sector. The metric tensor has a non-trivial running, even if
it is not quantized. The results are proved applying a certain map that
converts classical instabilities, due to higher derivatives, into classical
violations of causality, whose effects become observable at sufficiently high
energies. We study acausal Einstein-Yang-Mills theory with an R-dependent gauge
coupling in detail. We derive all-order formulas for the beta functions of the
dimensionality-six gravitational vertices induced by renormalization. Such beta
functions are related to the trace-anomaly coefficients of the matter
subsector.Comment: 36 pages; v2: CQG proof-corrected versio
A three-loop check of the 'a - maximization' in SQCD with adjoint(s)
The 'a - maximization' was introduced by K. Inrtiligator and B. Wecht for
finding anomalous dimensions of chiral superfields at the IR fixed points of
the RG flow. Using known explicit calculations of anomalous dimensions in the
perturbation theory of SQCD (with one or two additional adjoint fields), it is
checked here at the three-loop level.Comment: 5 pages; the title changed, the text improved and expande
Emerging materials fostering interdisciplinary collaboration in Materials Design
Materials Design is a recognized emerging and growing area in design practice and research that converges different fields and approaches to addressing a holistic perspective of materials in and for design. Therefore, it incorporates knowledge from various disciplines, like engineering and science. Direct interdisciplinary collaboration between engineers, scientists, artists and designers can benefit projects whose purpose is to bring innovation regarding materials and design. We assume this interdisciplinarity is a crucial practice for developing the emerging field of Materials Design with a sustainable and circular perspective. This article conveys the findings of an empirical collection of case studies on emerging materials and product design. The results demonstrate the sustainability and circularity orientations they present and different disciplinary cooperation to generate innovative outcomes. The authors examined ten European enterprises that present products driven by emerging materials
from alternative sources to support the statement. The paper identifies and reflects on the importance and value of collaboration. It aims to disseminate knowledge about the field of Materials Design and intends to highlight that interdisciplinary collaboration in this area can be favourable for achieving a sustainable paradigm and more responsible production and consumption patterns
A Field-theoretical Interpretation of the Holographic Renormalization Group
A quantum-field theoretical interpretation is given to the holographic RG
equation by relating it to a field-theoretical local RG equation which
determines how Weyl invariance is broken in a quantized field theory. Using
this approach we determine the relation between the holographic C theorem and
the C theorem in two-dimensional quantum field theory which relies on the
Zamolodchikov metric. Similarly we discuss how in four dimensions the
holographic C function is related to a conjectured field-theoretical C
function. The scheme dependence of the holographic RG due to the possible
presence of finite local counterterms is discussed in detail, as well as its
implications for the holographic C function. We also discuss issues special to
the situation when mass deformations are present. Furthermore we suggest that
the holographic RG equation may also be obtained from a bulk diffeomorphism
which reduces to a Weyl transformation on the boundary.Comment: 24 pages, LaTeX, no figures; references added, typos corrected,
paragraph added to section
The Gravity dual of the Non-Perturbative SUSY Yang-Mills Theory
The anomalous Ward identity is derived for SUSY Yang-Mills theories,
which is resulted out of Wrapping of branes on Supersymmetric two cycles.
From the Ward identity One obtains the Witten-Dijkgraaf-Verlinde-Verlinde
equation and hence can solve for the pre-potential. This way one avoids the
problem of enhancon which maligns the non-perturbative behaviour of the
Yang-Mills theory resulted out of Wrapped branes.Comment: 4 pages, LaTeX. Talk given at the IXth International Symposium on
Particles, Strings and Cosmology PASCOS '03, Mumbai-India, January 3-8 2003.
v2:some reference adde
Renormalization Group Flows from Five-Dimensional Supergravity
The use of gauged supergravity as a tool in studying the
AdS/CFT correspondence for Yang-Mills theory is reviewed. The
supergravity potential implies a non-trivial, supersymmetric IR fixed point,
and the flow to this fixed point is described in terms of a supergravity kink.
The results agree perfectly with earlier, independent field theory results. A
supergravity inspired -function, and corresponding -theorem is discussed
for general flows, and the simplified form for supersymmetric flows is also
given. Flows along the Coulomb branch of the Yang-Mills theory are also
described from the five-dimensional perspective.Comment: 12 pages, 3 figures; Latex, ioplppt.sty, iopl12.sty, epsf.sty.
Contribution to Strings `9
Weighted power counting, neutrino masses and Lorentz violating extensions of the Standard Model
We study the Standard-Model extensions that have the following features: they
violate Lorentz invariance explicitly at high energies; they are unitary,
local, polynomial and renormalizable by weighted power counting; they contain
the vertex (LH)^2, which gives Majorana masses to the neutrinos after symmetry
breaking, and possibly four fermion interactions; they do not contain
right-handed neutrinos, nor other extra fields. We study the simplest CPT
invariant Standard-Model extension of this type in detail and prove the
cancellation of gauge anomalies. We investigate the low-energy recovery of
Lorentz invariance and comment on other types of extensions.Comment: 26 pages; v2: more references and comments, PR
CFT/CFT interpolating RG flows and the holographic c-function
We consider holographic RG flows which interpolate between non-trivial
ultra-violet (UV) and infra-red (IR) conformal fixed points. We study the
``superpotentials'' which characterize different flows and discuss their
expansions near the fixed points. Then we focus on the holographic -function
as defined from the two-point function of the stress-energy tensor. We point
out that the equation for the metric fluctuations in the background flow is
equivalent to a scattering problem and we use this to obtain an expression for
the -function in terms of the associated Jost functions. We propose two
explicit models that realize UV-IR flows. In the first example we consider a
thin wall separating two AdS spaces with different radii, while in the second
one the UV region is replaced with an asymptotically AdS space. We find that
the holographic -function obeys the expected properties. In particular it
reduces to the correct -- nonzero -- central charge in the IR limit.Comment: 20 pages, discussion at the end of sec. 3 and sec. 4.1 change
The Four-Loop Konishi in N=4 SYM
We present the result of a full direct component calculation for the planar
four-loop anomalous dimension of the Konishi operator in N =4 Supersymmetric
Yang-Mills theory. Our result confirms the results obtained from superfield
(arXiv:0712.3522, arXiv:0806.2095) and superstring (arXiv:0807.0399)
computations, which take into account finite size corrections to the all-loop
asymptotic Bethe ansatz for the integrable models describing the spectrum of
the anomalous dimensions of the gauge-invariant operators and the spectrum of
the string states in the framework of the gauge/string duality.Comment: 7 pages, some detailes of calculations adde
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