/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 19 Let \(R\) be a ring with at leas... [FREE SOLUTION] | 91Ó°ÊÓ

91Ó°ÊÓ

Let \(R\) be a ring with at least two elements such that for every nonzero element \(a \in R\) there exists a unique element \(b \in R\) with \(a b a=a\). Show that (a) \(R\) has no zero divisors. (b) \(b a b=b\) (c) \(R\) has unity.

Short Answer

Expert verified
(a) Ring \(R\) has no zero divisors. (b) Element \(b\) satisfies \(bab = b\). (c) Ring \(R\) has a unity.

Step by step solution

01

Understanding Zero Divisors

Recall that a zero divisor in a ring is a nonzero element \(a\) for which there exists a nonzero element \(c\) such that \(ac = 0\). We will show that \(R\) has no zero divisors by assuming otherwise and reaching a contradiction.
02

Prove Part (a) - No Zero Divisors

Suppose for a contradiction that \(a\) and \(c\) are nonzero elements in \(R\) with \(ac = 0\). By hypothesis, there exists a unique \(b\) such that \(aba = a\). Consequently, \(ab = 1\) because if \(ab\) were zero, then \(a(ab)a = 0a = 0\), contradicting \(a(ab)a = a\). Hence, \(ab eq 0\). Thus, \(ac = 0\) implies that there are no nonzero divisors, proving no zero divisors exist.
03

Prove Part (b) - Verify the Property

Given that \(aba = a\), we also have \(bab\) to find. Multiply the equation \(aba = a\) on both sides by \(b\) to get \(abab = ab\). But since \(ab = 1\), \(ab = aba\), and thus \(babab = baba = b\). It follows that \(bab = b\).
04

Prove Part (c) - Existence of Unity

To show that \(R\) has a unity element, consider any nonzero element \(a\). Let \(b\) satisfy \(aba = a\). We want to show there exists an element \(e\) in \(R\) such that \(ae = ea = a\) for all \(a \in R\). Use \(a(ab) = a\) to deduce that \(ab = e\) serves as the identity for any arbitrary element shown by \(e \, e' = a, \, e'e = a\) for \(e,\, e' \), and \(e = e'\) proving that every element has an associate. All elements have a distinguished domain, thus \( R \) has a unity element.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!

Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Zero Divisors
In ring theory, zero divisors are elements that can multiply with a non-zero element to yield zero. Let's explore this concept in a friendly manner. Say you have a non-zero element \( a \); if there exists another non-zero element \( c \) such that \( ac = 0 \), then \( a \) and \( c \) are zero divisors. However, in the ring \( R \) given in our exercise, for every non-zero element \( a \), there exists a unique \( b \) such that \( aba = a \). This condition implies \( ab eq 0 \) because if \( ab = 0 \), then \( a(ba)a = 0 \), contradicting \( aba = a \). Therefore, \( R \) cannot have any zero divisors, as that would contradict the unique element property of the ring.
Unity Element
A unity element, also known as a multiplicative identity, is a special element in a ring that leaves other elements unchanged when multiplied. In simpler terms, this is like multiplying by 1 in a set of integers, where you have \( 1 \times n = n \times 1 = n \). In our ring \( R \), for each element \( a \), there exists a unique \( b \) such that \( aba = a \). By utilizing this relationship, we show that there is an element \( e \) such that for every element \( a \), the equation \( ae = ea = a \) holds.
  • Start by considering \( ab \) which acts akin to an identity since \( a(ab) = a \).
  • Because this holds for any non-zero \( a \), \( ab \) effectively becomes a unity for that element.
Hence, \( R \) indeed possesses a unity element, making it more harmonious in behavior.
Unique Element Property
This fascinating aspect of a ring refers to each non-zero element having a singular associate, \( b \), that fulfills the equation \( aba = a \). The idea here is beautifully tied to uniqueness; no different \( b \) could satisfy \( aba = a \) for the same \( a \), due to the uniqueness condition. This property means that for each \( a \), the operation "sandwiching" with \( b \) returns \( a \) back to its original form, almost like a perfect reflection. It forms a foundational aspect of proving our points about zero divisors and the unity element. It adds a layer of structure to the ring by ensuring predictable behavior of elements within the ring and eliminating contradictions that may otherwise arise in systems without such a property.
Algebraic Proofs
Algebraic proofs are the structured, logical steps taken to establish truths within mathematical structures. Here, each proof demonstrates a specific property of the ring \( R \) under examination:
  • Zero Divisors: By contradiction, you show no zero divisors can exist if for every element \( a \) in ring, unique \( b \) satisfies \( aba = a \).
  • Unity Element: By examining the relationship \( aba = a \) and deducing the existence of \( ab \) acting as an identity, the proofs reinforce the existence of a unity element.
  • Uniqueness: The unique association of each element to \( b \) forms the bedrock for many consecutively stacked deductions.
In solving mathematical problems in rings, one must weave through a tapestry of definitions, hypotheses, and logical deductions. Algebraic proofs offer the way to methodically confirm each aspect of the problem, leading to a satisfying conclusion where each element of \( R \) is perfectly understood and framed within the ring properties.

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Study anywhere. Anytime. Across all devices.