2,088 research outputs found
Emerging trends in entrepreneurial finance
The emergence of new sources of financing in the aftermath of the financial crisis has
substantially increased the funding options available to new entrepreneurial ventures.
Technology parks, startup incubators and accelerators, business angels and angel investment
organizations, equity crowdfunding platforms, venture capital funds, corporate
seed funds and institutional investors directly investing in new ventures, have significantly
increased the menu of funding channels, in many cases by leveraging the
disrupting effects of Fintech companies and the emergence of internet-based segments
of the capital market. As a consequence, a new financing eco-system for new ventures
has emerged in recent years that has significant implications for both investors and
entrepreneurs, impacting on entrepreneurial growth paths and creating new policy
challenges at both the national and global scales. The substantially larger set of funding
channels has not only been instrumental in the unprecedented growth in the number of
early stage companies but has also raised new questions that have challenged scholars
and practitioners and policymakers alike. Idiosyncratic risk-return profiles and investment
philosophies, unorthodox investment practices, innovative value-adding contributions
to portfolio companies ventures and structurally different exit options are some of
the areas that require urgent investigation.
The first \u201cEmerging Trends in Entrepreneurial Finance\u201d Conference, 1\u20132 June 2017 organized
by the Stevens School of Business, the University of Piemonte Orientale and the Editors
of Venture Capital: an International Journal of Entrepreneurial Finance at the Stevens Institute of
Technology (Hoboken, NJ, USA) with the sponsorship of Hanlon Financial Systems Center and
the Stevens Venture Center, aimed at gathering world-class scholars in the field of entrepreneurial
finance to stimulate a debate on the evolution of the financing ecosystem for new
ventures. From the close to 75 submissions, of which 16 were accepted for presentation. the
Guest Editors of this special Issue have selected six outstanding papers that address crucial
topics and recent developments
Exact Flow Equations and the U(1)-Problem
The effective action of a SU(N)-gauge theory coupled to fermions is evaluated
at a large infrared cut-off scale k within the path integral approach. The
gauge field measure includes topologically non-trivial configurations
(instantons). Due to the explicit infrared regularisation there are no gauge
field zero modes. The Dirac operator of instanton configurations shows a zero
mode even after the infrared regularisation, which leads to U_A(1)-violating
terms in the effective action. These terms are calculated in the limit of large
scales k.Comment: 22 pages, latex, no figures, with stylistic changes and some
arguments streamlined, typos corrected, References added, to appear in Phys.
Rev.
Exact Ward-Takahashi identity for the lattice N=1 Wess-Zumino model
The lattice Wess-Zumino model written in terms of the Ginsparg-Wilson
relation is invariant under a generalized supersymmetry transformation which is
determined by an iterative procedure in the coupling constant. By studying the
associated Ward-Takahashi identity up to order we show that this lattice
supersymmetry automatically leads to restoration of continuum supersymmetry
without fine tuning. In particular, the scalar and fermion renormalization wave
functions coincide.Comment: 6 pages, 5 figures, Talk given at QG05, Cala Gonone, Sardinia, Italy.
12-16 September 200
Caldera collapse and tectonics along the Main Ethiopian Rift: Reviewing possible relationships
The Main Ethiopian Rift (MER) represents an area where volcanism and tectonics interact to create closely linked volcano-tectonic features. This linkage is paramount in the axial portion of the rift, where magmatic segments localize several large peralkaline eruptive centres. Many of them evolved into caldera collapse (the best preserved of which are younger than ) generating large ignimbrites and registering the interaction between magmatism and tectonics along the MER. In this work we review the structure of the main collapsed calderas along the axial portion of the MER, to summarize the relationships between volcanism and tectonics proposed in the literature explaining their structural evolution. By doing this, we infer that tectonics had a strong influence in controlling the elongation of the majority of examined calderas. This control was induced by reactivation of inherited crustal fabrics or by stretching of the magma reservoirs under the MER regional stress field
SHMT1 and SHMT2 Are Functionally Redundant in Nuclear De novo Thymidylate Biosynthesis
The three enzymes that constitute the de novo thymidylate synthesis pathway in mammals, cytoplasmic serine hydroxymethyltransferase (SHMT1), thymidylate synthase (TYMS) and dihydrofolate reductase (DHFR) undergo sumoylation and nuclear import during S-phase. In this study, we demonstrate that purified intact mouse liver nuclei convert dUMP to dTMP in the presence of NADPH and serine. Neither nuclear extracts nor intact nuclei exposed to aminomethylphosphonate, a SHMT inhibitor, exhibit thymidylate synthesis activity. Nuclei isolated from Shmt1−/− mouse livers retained 25% of thymidylate synthesis activity exhibited by nuclei isolated from wild type mice. This residual activity was due to the presence of a cytoplasmic/nuclear isozyme of SHMT encoded by Shmt2. Shmt2 is shown to encode two transcripts, one which encodes a protein that localizes exclusively to the mitochondria (SHMT2), and a second transcript that lacks exon 1 and encodes a protein that localizes to the cytoplasm and nucleus during S-phase (SHMT2α). The ability of Shmt2 to encode a cytoplasmic isozyme of SHMT may account for the viability of Shmt1−/− mice and provide redundancy that permitted the expansion of the human SHMT1 L474F polymorphism that impairs SHMT1 sumoylation and nuclear translocation
Largely shared neural codes for biological and nonbiological observed movements but not for executed actions in monkey premotor areas
The neural processing of others' observed actions recruits a large network of brain regions (the action observation network; AON) in which frontal motor areas are thought to play a crucial role. As the discovery of mirror neurons (MNs) in the ventral premotor cortex, it has been assumed that their activation was conditional upon the presentation of biological rather than nonbiological motion stimuli, supporting a form of direct visuomotor matching. Nonetheless, nonbiological observed movements have rarely been used as control stimuli to evaluate visual specificity, thereby leaving the issue of similarity among neural codes for executed actions and biological or nonbiological observed movements unresolved. Here, we addressed this issue by recording from two nodes of the AON that are attracting increasing interest, namely, the ventrorostral part of the dorsal premotor area F2 and the mesial presupplementary motor area F6 of macaques while they 1) executed a reaching-grasping task, 2) observed an experimenter performing the task, and 3) observed a nonbiological effector moving in the same context. Our findings revealed stronger neuronal responses to the observation of biological than nonbiological movement, but biological and nonbiological visual stimuli produced highly similar neural dynamics and relied on largely shared neural codes, which in turn remarkably differed from those associated with executed actions. These results indicate that, in highly familiar contexts, visuomotor remapping processes in premotor areas hosting MNs are more complex and flexible than predicted by a direct visuomotor matching hypothesis
Deformed dimensional regularization for odd (and even) dimensional theories
I formulate a deformation of the dimensional-regularization technique that is
useful for theories where the common dimensional regularization does not apply.
The Dirac algebra is not dimensionally continued, to avoid inconsistencies with
the trace of an odd product of gamma matrices in odd dimensions. The
regularization is completed with an evanescent higher-derivative deformation,
which proves to be efficient in practical computations. This technique is
particularly convenient in three dimensions for Chern-Simons gauge fields,
two-component fermions and four-fermion models in the large N limit, eventually
coupled with quantum gravity. Differently from even dimensions, in odd
dimensions it is not always possible to have propagators with fully Lorentz
invariant denominators. The main features of the deformed technique are
illustrated in a set of sample calculations. The regularization is universal,
local, manifestly gauge-invariant and Lorentz invariant in the physical sector
of spacetime. In flat space power-like divergences are set to zero by default.
Infinitely many evanescent operators are automatically dropped.Comment: 27 pages, 3 figures; v2: expanded presentation of some arguments,
IJMP
Renormalization of the Hamiltonian and a geometric interpretation of asymptotic freedom
Using a novel approach to renormalization in the Hamiltonian formalism, we
study the connection between asymptotic freedom and the renormalization group
flow of the configuration space metric. It is argued that in asymptotically
free theories the effective distance between configuration decreases as high
momentum modes are integrated out.Comment: 22 pages, LaTeX, no figures; final version accepted in Phys.Rev.D;
added reference and appendix with comment on solution of eq. (9) in the tex
Time evolution of correlation functions and thermalization
We investigate the time evolution of a classical ensemble of isolated
periodic chains of O(N)-symmetric anharmonic oscillators. Our method is based
on an exact evolution equation for the time dependence of correlation
functions. We discuss its solutions in an approximation which retains all
contributions in next-to-leading order in a 1/N expansion and preserves time
reflection symmetry. We observe effective irreversibility and approximate
thermalization. At large time the system approaches stationary solutions in the
vicinity of, but not identical to, thermal equilibrium. The ensemble therefore
retains some memory of the initial condition beyond the conserved total energy.
Such a behavior with incomplete thermalization is referred to as "mesoscopic
dynamics". It is expected for systems in a small volume. Surprisingly, we find
that the nonthermal asymptotic stationary solutions do not change for large
volume. This raises questions on Boltzmann's conjecture that macroscopic
isolated systems thermalize.Comment: 40 pages, 9 figure
Exact and Truncated Dynamics in Nonequilibrium Field Theory
Nonperturbative dynamics of quantum fields out of equilibrium is often
described by the time evolution of a hierarchy of correlation functions, using
approximation methods such as Hartree, large N, and nPI-effective action
techniques. These truncation schemes can be implemented equally well in a
classical statistical system, where results can be tested by comparison with
the complete nonlinear evolution obtained by numerical methods. For a 1+1
dimensional scalar field we find that the early-time behaviour is reproduced
qualitatively by the Hartree dynamics. The inclusion of direct scattering
improves this to the quantitative level. We show that the emergence of
nonthermal temperature profiles at intermediate times can be understood in
terms of the fixed points of the evolution equations in the Hartree
approximation. The form of the profile depends explicitly on the initial
ensemble. While the truncated evolution equations do not seem to be able to get
away from the fixed point, the full nonlinear evolution shows thermalization
with a (surprisingly) slow relaxation.Comment: 30 pages with 12 eps figures, minor changes; to appear in Phys.Rev.
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