68 research outputs found
Dynamical SUSY and R-symmetry breaking in SQCD with massive and massless flavors
We show that supersymmetry and R-symmetry can be dynamically broken in a
long-lived metastable vacuum of SQCD with massive and massless flavors. The
vacuum results from a competition of a (leading) two-loop effect and small
"Planck" suppressed higher-dimension operators. This mechanism provides a
particularly simple realization of dynamical SUSY and R-symmetry breaking, and
as such it is a good starting point for building phenomenologically viable
models of gauge mediation. We take a preliminary step in this direction by
constructing a complete model of minimal gauge mediation. Here we find that the
parameters of the model are surprisingly constrained by the hidden sector.
Similar mechanisms for creating long-lived states operate in a large class of
models.Comment: 25 pages. v2: added references, minor correctio
Strings from Massive Higher Spins: The Asymptotic Uniqueness of the Veneziano Amplitude
We consider weakly-coupled theories of massive higher-spin particles. This
class of models includes, for instance, tree-level String Theory and Large-N
Yang-Mills theory. The S-matrix in such theories is a meromorphic function
obeying unitarity and crossing symmetry. We discuss the (unphysical) regime
, in which we expect the amplitude to be universal and exponentially
large. We develop methods to study this regime and show that the amplitude
necessarily coincides with the Veneziano amplitude there. In particular, this
implies that the leading Regge trajectory, , is asymptotically linear in
Yang-Mills theory. Further, our analysis shows that any such theory of
higher-spin particles has stringy excitations and infinitely many
asymptotically parallel subleading trajectories. More generally, we argue that,
under some assumptions, any theory with at least one higher-spin particle must
have strings.Comment: 44 pages, 5 figure
Spin-strain coupling in nanodiamonds
Fluorescent nanodiamonds have been used to a large extent in various
biological systems due to their robust nature, inert properties and the
relative ease of modifying their surface for attachment to different functional
groups. Within a given batch, however, each nanodiamond is indistinguishable
from its neighbors and so far one could only rely on fluorescence statistics
for some global information about the ensemble. Here, we propose and measure
the possibility of adding another layer of unique information, relying on the
coupling between the strain in the nanodiamond and the spin degree-of-freedom
in the nitrogen-vacancy center in diamond. We show that the large variance in
axial and transverse strain can be encoded to an individual radio-frequency
identity for a cluster of nanodiamonds. When using single nanodiamonds, this
unique fingerprint can then be potentially tracked in real-time in, e.g.,
cells, as their size is compatible with metabolism intake. From a completely
different aspect, in clusters of nanodiamonds, this can already now serve as a
platform for anti-counterfeiting measures.Comment: SI with interesting qrcode is available at
https://www.dropbox.com/s/5gjwfegiydxr5ig/SI.pd
Relevance in the Renormalization Group and in Information Theory
The analysis of complex physical systems hinges on the ability to extract the
relevant degrees of freedom from among the many others. Though much hope is
placed in machine learning, it also brings challenges, chief of which is
interpretability. It is often unclear what relation, if any, the architecture-
and training-dependent learned "relevant" features bear to standard objects of
physical theory. Here we report on theoretical results which may help to
systematically address this issue: we establish equivalence between the
information-theoretic notion of relevance defined in the Information Bottleneck
(IB) formalism of compression theory, and the field-theoretic relevance of the
Renormalization Group. We show analytically that for statistical physical
systems described by a field theory the "relevant" degrees of freedom found
using IB compression indeed correspond to operators with the lowest scaling
dimensions. We confirm our field theoretic predictions numerically. We study
dependence of the IB solutions on the physical symmetries of the data. Our
findings provide a dictionary connecting two distinct theoretical toolboxes,
and an example of constructively incorporating physical interpretability in
applications of deep learning in physics
Relevance in the Renormalization Group and in Information Theory
The analysis of complex physical systems hinges on the ability to extract the relevant degrees of freedom from among the many others. Though much hope is placed in machine learning, it also brings challenges, chief of which is interpretability. It is often unclear what relation, if any, the architecture- and training-dependent learned “relevant” features bear to standard objects of physical theory. Here we report on theoretical results which may help to systematically address this issue: we establish equivalence between the field-theoretic relevance of the renormalization group, and an information-theoretic notion of relevance we define using the information bottleneck (IB) formalism of compression theory. We show analytically that for statistical physical systems described by a field theory the relevant degrees of freedom found using IB compression indeed correspond to operators with the lowest scaling dimensions. We confirm our field theoretic predictions numerically. We study dependence of the IB solutions on the physical symmetries of the data. Our findings provide a dictionary connecting two distinct theoretical toolboxes, and an example of constructively incorporating physical interpretability in applications of deep learning in physics
CONTROL ALGORITHMS FOR GROUPS OF KINEMATIC UNICYCLE AND SKID-STEERING MOBILE ROBOTS WITH RESTRICTED INPUTS
Abstract. The paper presents analytical and practical studies concerning the control problems of a group of Wheeled Mobile Robots (WMRs) subject to physical constraints. Firstly, controllers for achieving trajectory tracking for kinematic unicycle-like and skidsteering mobile robots with restricted control inputs are established. Next, the underlying tracking controllers are applied for group control under the condition of actuator constraints. In particular we are developing control strategies for establishing rigid and convoy-like formations for vehicles with bounded inputs. The group control approach is based on the concepts of virtual robot and virtual formation. The proposed controllers employ smooth bounded functions that can easily be realized. The performance of the resulting controllers are demonstrated by means of numerical and simulation results
Quantum circuits measuring weak values, Kirkwood--Dirac quasiprobability distributions, and state spectra
Weak values and Kirkwood--Dirac (KD) quasiprobability distributions have been
independently associated with both foundational issues in quantum theory and
advantages in quantum metrology. We propose simple quantum circuits to measure
weak values, KD distributions, and spectra of density matrices without the need
for post-selection. This is achieved by measuring unitary-invariant, relational
properties of quantum states, which are functions of Bargmann invariants, the
concept that underpins our unified perspective. Our circuits also enable
experimental implementation of various functions of KD distributions, such as
out-of-time-ordered correlators (OTOCs) and the quantum Fisher information in
post-selected parameter estimation, among others. An upshot is a unified view
of nonclassicality in all those tasks. In particular, we discuss how negativity
and imaginarity of Bargmann invariants relate to set coherence.Comment: 23+7 pages, 7+5 figures. v2: new sections 2.3, 2.4, 3, 4.5, revised
structure. Comments are welcome
Quantum circuits for measuring weak values, Kirkwood–Dirac quasiprobability distributions, and state spectra
Weak values and Kirkwood–Dirac (KD) quasiprobability distributions have been independently associated with both foundational issues in quantum theory and advantages in quantum metrology. We propose simple quantum circuits to measure weak values, KD distributions, and spectra of density matrices without the need for post-selection. This is achieved by measuring unitary-invariant, relational properties of quantum states, which are functions of Bargmann invariants, the concept that underpins our unified perspective. Our circuits also enable experimental implementation of various functions of KD distributions, such as out-of-time-ordered correlators (OTOCs) and the quantum Fisher information in post-selected parameter estimation, among others. An upshot is a unified view of nonclassicality in all those tasks. In particular, we discuss how negativity and imaginarity of Bargmann invariants relate to set coherence
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