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Corporate Acquisitions and Firm-level Uncertainty: Domestic versus Cross-Border Deals
This paper studies the impact of corporate acquisitions on the uncertainty faced by acquiring firms. We use data for UK public companies from 2004 to 2017 and employ a matching estimator combined with difference-in-differences to control for the endogenous selection of firms into acquiring status. Acquisitions exert a large and persistent effect on the volatility of stock returns of acquirers and is characterized by a pecking order: domestic takeovers lead to a reduction in the uncertainty faced by the acquirer, while cross-border acquisitions|particularly those involving target firms in emerging markets|engender a positive response in acquirers' volatility
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Quadratic ideals and Rogers–Ramanujan recursions
We give an explicit recursive description of the Hilbert series and Gröbner bases for the family of quadratic ideals defining the jet schemes of a double point. We relate these recursions to the Rogers–Ramanujan identity and prove a conjecture of the second author, Oblomkov and Rasmussen
The Jackprot Simulation Couples Mutation Rate with Natural Selection to Illustrate How Protein Evolution Is Not Random
Protein evolution is not a random process. Views which attribute randomness to molecular change, deleterious nature to single-gene mutations, insufficient geological time, or population size for molecular improvements to occur, or invoke “design creationism” to account for complexity in molecular structures and biological processes, are unfounded. Scientific evidence suggests that natural selection tinkers with molecular improvements by retaining adaptive peptide sequence. We used slot-machine probabilities and ion channels to show biological directionality on molecular change. Because ion channels reside in the lipid bilayer of cell membranes, their residue location must be in balance with the membrane’s hydrophobic/philic nature; a selective “pore” for ion passage is located within the hydrophobic region. We contrasted the random generation of DNA sequence for KcsA, a bacterial two-transmembrane-domain (2TM) potassium channel, from Streptomyces lividans, with an under-selection scenario, the “jackprot,” which predicted much faster evolution than by chance. We wrote a computer program in JAVA APPLET version 1.0 and designed an online interface, The Jackprot Simulation http://faculty.rwu.edu/cbai/JackprotSimulation.htm, to model a numerical interaction between mutation rate and natural selection during a scenario of polypeptide evolution. Winning the “jackprot,” or highest-fitness complete-peptide sequence, required cumulative smaller “wins” (rewarded by selection) at the first, second, and third positions in each of the 161 KcsA codons (“jackdons” that led to “jackacids” that led to the “jackprot”). The “jackprot” is a didactic tool to demonstrate how mutation rate coupled with natural selection suffices to explain the evolution of specialized proteins, such as the complex six-transmembrane (6TM) domain potassium, sodium, or calcium channels. Ancestral DNA sequences coding for 2TM-like proteins underwent nucleotide “edition” and gene duplications to generate the 6TMs. Ion channels are essential to the physiology of neurons, ganglia, and brains, and were crucial to the evolutionary advent of consciousness. The Jackprot Simulation illustrates in a computer model that evolution is not and cannot be a random process as conceived by design creationists
On the Quantum Chromodynamics of a Massive Vector Field in the Adjoint Representation
In this paper, we explore the possibility of constructing the quantum
chromodynamics of a massive color-octet vector field without introducing higher
structures like extended gauge symmetries, extra dimensions or scalar fields.
We show that gauge invariance is not enough to constraint the couplings.
Nevertheless the requirement of unitarity fixes the values of the coupling
constants, which otherwise would be arbitrary. Additionally, it opens a new
discrete symmetry which makes the coloron stable and avoid its resonant
production at a collider. On the other hand, a judicious definition of the
gauge fixing terms modifies the propagator of the massive field making it
well-behaved in the ultra-violet limit. The relation between our model and the
more general approach based on extended gauge symmetries is also discussed.Comment: Subsection 2.1 rewritten in order to make it more pedagogical. This
version match the text accepted in IJMP
The Planck Scale from Top Condensation
We propose a scenario in which the Planck scale is dynamically linked to the
electroweak scale induced by top condensation. The standard model field
content, without the Higgs, is promoted to a 5D warped background. There is
also an additional 5D fermion with the quantum numbers of the right-handed top.
Localization of the zero-modes leads, at low energies, to a Nambu-Jona-Lasinio
model that also stabilizes the radion field dynamically thus explaining the
hierarchy between the Planck scale and v_EW = 174 GeV. The top mass arises
dynamically from the electroweak breaking condensate. The other standard model
fermion masses arise naturally from higher-dimension operators, and the fermion
mass hierarchies and flavor structure can be explained from the localization of
the zero-modes in the extra dimension. If any other contributions to the radion
potential except those directly related with electroweak symmetry breaking are
engineered to be suppressed, the KK scale is predicted to be about two orders
of magnitude above the electroweak scale rendering the model easily consistent
with electroweak precision data. The model predicts a heavy (composite) Higgs
with a mass of about 500 GeV and standard-model-like properties, and a
vector-like quark with non-negligible mixing with the top quark and mass in the
1.6 - 2.9 TeV range. Both can be within the reach of the LHC. It also predicts
a radion with a mass of a few GeV that is very weakly coupled to standard model
matter.Comment: 41 pages, 7 figures; added references, minor changes in the
electroweak precision constraints section; final version in PR
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