367 research outputs found
High-Precision Calculations in Strongly Coupled Quantum Field Theory with Next-to-Leading-Order Renormalized Hamiltonian Truncation
Hamiltonian Truncation (a.k.a. Truncated Spectrum Approach) is an efficient
numerical technique to solve strongly coupled QFTs in d=2 spacetime dimensions.
Further theoretical developments are needed to increase its accuracy and the
range of applicability. With this goal in mind, here we present a new variant
of Hamiltonian Truncation which exhibits smaller dependence on the UV cutoff
than other existing implementations, and yields more accurate spectra. The key
idea for achieving this consists in integrating out exactly a certain class of
high energy states, which corresponds to performing renormalization at the
cubic order in the interaction strength. We test the new method on the strongly
coupled two-dimensional quartic scalar theory. Our work will also be useful for
the future goal of extending Hamiltonian Truncation to higher dimensions d >=
3.Comment: 8 pages, 4 figures; v2: published versio
NLO Renormalization in the Hamiltonian Truncation
Hamiltonian Truncation (a.k.a. Truncated Spectrum Approach) is a numerical
technique for solving strongly coupled QFTs, in which the full Hilbert space is
truncated to a finite-dimensional low-energy subspace. The accuracy of the
method is limited only by the available computational resources. The
renormalization program improves the accuracy by carefully integrating out the
high-energy states, instead of truncating them away. In this paper we develop
the most accurate ever variant of Hamiltonian Truncation, which implements
renormalization at the cubic order in the interaction strength. The novel idea
is to interpret the renormalization procedure as a result of integrating out
exactly a certain class of high-energy "tail states". We demonstrate the power
of the method with high-accuracy computations in the strongly coupled
two-dimensional quartic scalar theory, and benchmark it against other existing
approaches. Our work will also be useful for the future goal of extending
Hamiltonian Truncation to higher spacetime dimensions.Comment: 28pp + appendices, detailed version of arXiv:1706.0612
Warped Phenomenology of Higher-Derivative Gravity
We examine the phenomenological implications at colliders for the existence
of higher-derivative gravity terms as extensions to the Randall-Sundrum model.
Such terms are expected to arise on rather general grounds, e.g., from string
theory. In 5-d, if we demand that the theory be unitary and ghost free, these
new contributions to the bulk action are uniquely of the Gauss-Bonnet form. We
demonstrate that the usual expectations for the production cross section and
detailed properties of graviton Kaluza-Klein resonances and TeV-scale black
holes can be substantially altered by existence of these additional
contributions. It is shown that measurements at future colliders will be highly
sensitive to the presence of such terms.Comment: 29 pages, 8 figure
Observers and Measurements in Noncommutative Spacetimes
We propose a "Copenhagen interpretation" for spacetime noncommutativity. The
goal is to be able to predict results of simple experiments involving signal
propagation directly from commutation relations. A model predicting an energy
dependence of the speed of photons of the order E/E_Planck is discussed in
detail. Such effects can be detectable by the GLAST telescope, to be launched
in 2006.Comment: 10 pp; v2: equivalence of observers explicitely stated; v3: minor
changes, references and remarks added, burst spreading with energy emphasized
as a signature rather than nois
Collider Production of TeV Scale Black Holes and Higher-Curvature Gravity
We examine how the production of TeV scale black holes at colliders is
influenced by the presence of Lovelock higher-curvature terms in the action of
models with large extra dimensions. Such terms are expected to arise on rather
general grounds, e.g., from string theory and are often used in the literature
to model modifications to the Einstein-Hilbert action arising from quantum
and/or stringy corrections. While adding the invariant which is quadratic in
the curvature leads to quantitative modifications in black hole properties,
cubic and higher invariants are found to produce significant qualitative
changes, e.g., classically stable black holes. We use these higher-order
curvature terms to construct a toy model of the black hole production cross
section threshold. For reasonable parameter values we demonstrate that detailed
measurements of the properties of black holes at future colliders will be
highly sensitive to the presence of the Lovelock higher-order curvature terms.Comment: 37 pages, 11 figures, references adde
New DRIE-Patterned Electrets for Vibration Energy Harvesting
This paper is about a new manufacturing process aimed at developing stable
SiO2/Si3N4 patterned electrets using a Deep Reactive Ion Etching (DRIE) step
for an application in electret-based Vibration Energy Harvesters (e-VEH). This
process consists in forming continuous layers of SiO2/Si3N4 electrets in order
to limit surface conduction phenomena and is a new way to see the problem of
electret patterning. Experimental results prove that patterned electrets
charged by a positive corona discharge show excellent stability with high
surface charge densities that may reach 5mC/m^2 on 1.1\mu m-thick layers, even
with fine patterning and harsh temperature conditions (up to 250{\deg}C). This
paves the way to new e-VEH designs and manufacturing processes.Comment: Proc. European Energy Conference, 201
Radiation Problem in Transplanckian Scattering
We investigate hard radiation emission in small-angle transplanckian
scattering. We show how to reduce this problem to a quantum field theory
computation in a classical background (gravitational shock wave). In momentum
space, the formalism is similar to the flat-space light cone perturbation
theory, with shock wave crossing vertices added. In the impact parameter
representation, the radiating particle splits into a multi-particle virtual
state, whose wavefunction is then multiplied by individual eikonal factors. As
a phenomenological application, we study QCD radiation in transplanckian
collisions of TeV-scale gravity models. We derive the distribution of initial
state radiation gluons, and find a suppression at large transverse momenta with
respect to the standard QCD result. This is due to rescattering events, in
which the quark and the emitted gluon scatter coherently. Interestingly, the
suppression factor depends on the number of extra dimensions and provides a new
experimental handle to measure this number. We evaluate the leading-log
corrections to partonic cross-sections due to the initial state radiation, and
prove that they can be absorbed into the hadronic PDF. The factorization scale
should then be chosen in agreement with an earlier proposal of Emparan, Masip,
and Rattazzi. In the future, our methods can be applied to the gravitational
radiation in transplanckian scattering, where they can go beyond the existing
approaches limited to the soft radiation case.Comment: 41 pp, v2: minor changes and added refs, conforms with published
versio
Ethnic model of consumer practices tatars and Russians of republic of tatarstan in the period of globalization
© 2015, Review of European Studies. All right reserved. The purpose of this article is the comparative analysis of models of consumer practices of Tatars and Russians of the multiethnic region (Republic of Tatarstan, Russia) in the situation of globalization of consumer culture. The problem of modeling consumer practices of ethnic groups considered in the concept of economic anthropology (ethnology). It is concluded that a combination of two opposing processes within consumer practices of ethnic groups in the context of globalization: the erosion of ethno-cultural space and the revival of ethnic and cultural traditions. Value profiles of consumers working age of two ethnic groups of Tatarstan-Tatars and Russians, using the technique of LOV (List of Values), are constructed. Also value profiles further investigated by gender. Constructed value profiles of Tatars and Russians is one of the elements of the model of consumer practices of these ethnic groups. Consumer practices are constantly under the influence of external and internal factors, and their systematic study is the task of further work. Regular monitoring of the dynamics of the consumer practices of ethnic groups allows to monitor the socio-cultural and socio-economic processes in the interests of both the market subjects as well as various social groups
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